Exactly. When you're on that tight a deadline, ANY failed check is going to be a big deal.
The Diplomat fails a Negotiation roll to get some allies? Your potential forces are cut in half;
The Engineer fails a Mechanics check to soup-up the defenses? Your fortification have become very easy to breach.
The Commander fails a check to set up a battle plan? Hours are lost in pointless bickering over tactics and the Empire will have an easier time walking all over you.
Since the article mentions that the planets are all very close together I doubt you'll lose more than ~5 or 6 hours on a failed Astrogation check. But when that's 1/8 of your total time, well...you may have to cut a stop or two out of your planned route to make it back in time. Which ones can you afford to sacrifice, and which are too important to let go...?