I was thinking about how the morality rules might function a bit differently than intended for groups that play games that are longer/shorter than "normal". Basically, you accumulate conflict over the course of a session then at the end, the amount of conflict you generated, combined with a d10 role, determines how your morality changes. However I didn't see anything specifying how long a session the rules had in mind, whether in terms of hours, scenes, encounters, etc.

Basically, my concern is that groups that play shorter games can get away with a bit more evil without their morality score dropping because they get the d10 roles more often in terms of "in-universe" time. Meanwhile, groups that play longer games wouldn't get those end-of-session d10 roles as often in terms of "in-universe" time, so their conflict-generating actions could have a greater impact.

Maybe this isn't a big deal. What are some things that groups could do to mitigate this, if they so desired? The obvious thing would be to role the d10 more or less than once per session, but some guidelines for what the RAW expects a session to be would be nice.

Generally a session in this hobby is considered about four hours, give or take. If your games run longer or shorter you should adjust accordingly.

What are some things that groups could do to mitigate this, if they so desired?

Resolve Conflict at the end of the adventure, not the session, unless your sessions are adventure-length.

As mouthymerc above notes, the standard adventure length is about four hours of play -- an arbitrary length of time that's grown organically out of convention play, yet it remains useful nonetheless as many published adventures (in nearly all RPGs now) are written with that timeframe in mind. So, if your sessions are short, and it takes you two sessions to get through an adventure, don't resolve Conflict after the first session -- wait until the adventure is over in the second.

Now, if your adventures are short, that is, they have fewer scenes because you're writing (or adapting) adventures designed to fit into a shorter session, then I would recommend just using a smaller die than a d10 (e.g.: a d8 if it's 3 hours, d6 for 2). This would also be applicable to GM's that tend to run longer adventures, spanning many sessions, broken down into chapters that will fit into a single session.

Full agreement with Lorne if you want to change the dice, but I feel like the d10 mechanic suitably compensates for any length of session time. It's half a mind game: sure, chances are you'll roll somewhere around a 5 and mitigate low-level Conflict, but all gamers are forever aware of rolling a 1. That concern will probably motivate players to seek the least Conflict possible, no matter how long your session runs.

I have to say... maybe it's just my group, but we never get an "adventure" done in just 4 hours. Ever.

The EotE Beginner Game took two sessions and both of those ran towards 6 hours... but then we kvetch, run off the rails, run back onto the rails, run into the train on the other track, blow up that train, steal it's cargo, then finally get back to the adventure at hand...

If your sessions run particularly long I'd just look for a logical point around 4 hours to do a tabulation. Perhaps at a scene or chapter break, or after a major encounter.