Another thing is that, while you still need to get adequate sleep (particularly for whoever is driving, since they have to be awake to do so, unlike those on the bus/train tours who can grab a nap while riding), the long daylight hours do also allow you to see more than you would many places.
For instance, while the bus tours going into Denali can be 8 or more hours (depending on how far you want to go into the park on the 90ish mile road, which is mostly dirt/stone and sharp turns, so speeds are slow), they will start as early as 5am
Thus you can have an 8 hour tour and still be done by early afternoon, allowing for you to work in something else as well, which would not be feasible in too many places you travel to with more "normal" days.