of course...
anyway, how many times would you repeat a leveling instance? you know the answer: not many, because after a while you will outlevel it....
for endgame content, you don't have this "problem"... you may eventually get bored of some of them, but there are so many lvl 80 dungeons!!
so, if i was planning to get a group of friends to make instances together, i would think about the best setup for the hardest endgame instances...