Maxing uot your Aeons in FFX is supposed to take 500 hours in and of itself I believe. Add to that anpther 150-250 hours of the game+getting celestial weapons+maxing stats, it's quite possible to a create a game with many hundreds of hours 'activities'. I say activities because I can't see how farming items to upgrade characters can count as real gameplay.
Nah it's not that much... I put about 180 hours in the game and it was pretty drained... Really nothing more you could do or max out... Then again, i didn't max out ALL the characters, i'm sure i left a couple out...