I think it depends on several factors.
* What type of game are we talking about? I'll accept longer cutscenes in a Final Fantasy game than in an action-packed FPS, for example.
* Can it be skipped? If so, I don't mind if it's 10 mins long (unless it sucks...), because I know that next time, I won't have to watch it. Most cutscenes are fine, as long as I don't have to watch them over and over again.
* Where in the game is it? If it interrupts gameplay in the middle of a fun part of the game, it had better be short!
* Is the cutscene actually necessary? Does it add something to the game besides eye-candy (if that)? Does it present something important (character, area...)? Does it move the story forward more effectively than what could be achieved within the normal gameplay mode? If it's just the devs saying "look what I can do with 3DSMax!", then I won't put up with it for very long.
* Is it good? Is it well written? Does it keep me interested, or does it bore me? The better it is, the longer it can be.
So basically... I can't answer the question with any alternative provided.