I'll quit a game over difficulty too, but I'll do it if it's too easy. I understand that we challenge gamers are rare, but I'm hardly alone. I just don't understand why developers have abandoned difficulty levels that allow gamers of all skill levels to play your game. Increasing the health of the enemies isn't enough -- the game is still just as easy, but it takes longer to win. I'm talking true difficulty levels.
I prefer one difficulty level. Well-balanced to require some proficiency to complete the game. With added objectives/achievements that require you to master the gameplay mechanics. I'm ok with a second easy difficulty if you make it clear that it's not the preferred experience. I mean if a game has like 5 difficulty levels how do you know what the 'real' experience is. I hate 'nightmare' difficulties that are designed with the goal of being pretty much impossible.
As for game length, aside from RPGs which kind of march to their own drum, I think the sweet spot for game length is about 8 hours for the core experience. When games get much longer than that I almost always feel the 'padding'. I'd rather have a tighter and shorter experience if that's the trade-off. Also I probably dig short games a little more these days because I know my backlog of games is probably measured in thousands of hours.