A feasible cold-sleep system would solve a lot of these. As it means it matters a lot less how long it takes to get somewhere.

I was reading "A Deepness in the Sky" by Vernor Vinge the other day, and his portrayal of that was pretty good. Basically on a long trip the crew cycles being awake and "on watch". So there are always some people awake to deal with problems, but everyone only has to expend a year or two of their lifespan on the trip. (As an aside, great book)