Probably no more than 1-2 naps per day to maintain that it's a unique creature trait. Otherwise its GM call. I suppose if the species doesn't offer a related game mechanism for the sleep cycle you could easily argue that they still need 8 hours a day, just split up into the four 2-hour naps.

I would say if the lack of sleep rules are going to be necessary for your campaign then decide ahead of time if you want the Chadra-Fan player to have to roll checks normally like other players, or if he's going to have an advantage due to his species.

Considering how unlikely most DMs are to use the sleep deprivation rules, its probably not surprising that FFG wouldn't bother coming up with a special mechanism that would only apply to that very rare instance that its actually used (if at all). I've been running games for about two years now, and I've never put my players in that situation yet.

The ability to only need 2 hours of sleep per day would be listed as a Species special ability in the stat block if it were intended for use. It's not. For reference note that even the Droid "species" is called out as requiring "rest."

Wookiepedia and the "Essential" guides are fluff pieces that can provide context, but are not game rules, do not take into account game balance requirements, and (sadly) often have errors and exaggerations that can muddy waters and make trivial items and people the most important thing in the galaxy.

So your questions:

So do Chadra-Fan sleep once a day for a total of 2 hours?

or

Do they sleep four times a day for a total of 8 hours?

Chadra-fan Species stat block doesn't list it as an ability so no, Chadra-Fan need 6-8 hours of rest like everyone else, they just typically prefer to take it in 3-4 two hour naps instead of all at once.

Are there any rules related to sleeping and resting that we are missing?

The hard rule is not getting a full nights rest will prevent the character from recovering full strain.

The soft rule on sleep deprivation is the GM could apply any setback or difficulty increase he finds appropriate based on the situation and the result of other checks, apply additional strain, and apply other appropriate penalties should they wish. (So basically just like everything else that can affect the characters).

Do races that require less than 8 hours of sleep gain any more time for activities that require checks? Do they gain any mechanical benefit in the game?

Species that require less, or no sleep would be able to go a few hours longer before the negative effects of sleep deprivation start to take hold, or ignore them entirely respectively. How this actually translates over to the game is up to your GM and will depend heavily on how Adventures are run. Like food, water, and docking fees, sleep is just as likely to be handwaved as hard tracked, so taking a species specifically to ignore sleep isn't a sure-fire thing.

Though it should be noted that if a Species requires say 3 hours of sleep every 24 hours, then after missing it they'll be in the exact same boat as an 8 hour sleeper that missed sleepy time. So really it's only the benefit of the difference between a normal humanoid and the reduced sleep, they can't make the argument that because they only need 3 hours of sleep that somehow means sleep deprivation wouldn't hit them as hard.

To Ghostofman,

Where in the books does it state that full nights rest is 6 to 8 hours? All I find are vague statements with no time requirement attached to them.

Other RPGs that I have played have a stated hard requirement for a full rest but I haven't found one in this game. I would love to have such a limit stated clearly in the rules if I can because the game I am in is dealing with activities like crafting and repairs that have time requirements.

Personally, I'd assume they need the same rest in total as anyone else. However, if there were a situation where they had to stand watch, or go at a pace where I might be giving other folks setbacks to normal tasks (the Battlestar Galactic episode: 22 comes to mind), I might not give them to the Chadra-Fan. If there is a Resilience check or Vigilance check for standing watch to notice sometihng while forgoing sleep, I might give the Chadra Fan boosts (or at least fewer setback) to the check.

Note that in both of these cases, I usually put the burden of remembering that on the player, as a way to reward having some knowledge about their species and trying to play them appropriately. But if htey can say hey, my species is known for X, I will often throw a boost or perhaps remove a setback for that. Not always, but often.

To Ghostofman,

Where in the books does it state that full nights rest is 6 to 8 hours? All I find are vague statements with no time requirement attached to them.

Other RPGs that I have played have a stated hard requirement for a full rest but I haven't found one in this game. I would love to have such a limit stated clearly in the rules if I can because the game I am in is dealing with activities like crafting and repairs that have time requirements.

Welcome to the FFG Star Wars game, where little details don't matter except when they do!

Seriously though, a "full nights rest" among many many other things, is left up to the GM for interpretation in this system. When FFG laid out the groundwork for this system they decided to focus on making a game with a cinematic feel, so lots of little details that generally don't matter day-to-day were just left up to GM interpretation, allowing for a Story-first design. Since 6-8 hrs is the "normal" for most real humans, it's probably safe to say that translates to Star Wars Humans (and other similar species) as well.

Other systems, especially those with a more crunchy dungeon crawl base, will do things like define how long you need to sleep because that's a bigger part of the mechanic as often things like spells and abilities will be defined as "once daily" or require some other time thing to prevent their continuous use. When you're mid dungeon crawl and have set up camp 30 levels underground with angry monsters wondering around, tracking if you can get enough sleep may be an issue.

Star Wars on the other hand is more of a story driven game, there's some kind of adventure across the cosmos the characters are on and little details like lunch, sleep, docking fees, water, a round at the cantina, exactly how many bootleg Palpatine Bobbleheads are in "a crate" and how many Enc that comes out to, and so on are largely irrelevant unless there's a story element to make it so. Essentially it's more like a movie or TV show, where you rarely see the characters actually sleep, or eat, or pump gas, or use the bathroom. Just because you never see Chewie unleash a katarn in the Falcon's head, doesn't mean it don't happen, just that nothing important happens in there (well, nothing important to anyone except Chewie and the next person to use the head anyway).

If the Adventure is a Con Job to steal a priceless artifact, you can probably assume there's enough time for the players to get "a full nights rest" for every "day" because the point of the story isn't the character being exhausted. If the adventure is the players have been shot down in Imperial territory and need to avoid search teams and hungry super predators while getting to a pickup point in a specific time frame, how long a player sleeps is a thing because a major theme of the adventure is the shortage of every resource possible, which includes rest.

And as Mr Kappel points out, just because it ain't 2 hours per day doesn't mean the Chadra-fan can't still make it work. By splitting up his sleep cycle into 2 hour naps, the guy has options that might allow him to delay or bypass a sleep depriving situation and/or help the entire party avoid it by leveraging his 2 hour naps.

Of course, leaving the Chadra-Fan in the ship cockpit alone to watch for that ship you're waiting on to ambush carries with it its own problems. A chadra-fan would likely see that as the perfect opportunity to take apart the sensor array to make some special modifications, so that it's not really working at all when its time to launch the attack.

To my mind, crafting times are best used in conjunction with hard deadlines to stress players with prioritization. If it's going to take 72 hours to repair the gizmo on the ship, but they need to break orbit in 60 hours in order to start/complete a mission, then they have hard choices to make. Similarly, if the party leverages the Chadra-Fan's ability to get rest in several small chunks, then that being will invariably be on watch when the excrement strikes the air circulator. After the second or third time, things like "unlucky" or "inattentive" or even "traitor" might get bandied about.

Ghostofman, that bit about Chewie in the 'fresher had me crying, I was laughing so hard! I need more coffee...