With the different body types, classes and different skills to obtain plus the customization, I think this game would last me awhile as an offline single-player game. If it's anything like Halo: Reach, then it would take me many, many months, since I do not have much time to play games, so the game-time would be dragged out/extended for me immensely. ^_^
I avoid online, so DLC's are out of the question. (Sometimes I wait for the GOTY edition for some games because of this.)
I play about once or twice or, at most, three times a week (on weekends only which may including Friday) and only for a couple of hours, so obviously this could be why I almost never finish games and play them for several years, lol!
Too bad there's no offline co-op, though. I would have loved to play with both of my sisters and occasional cousins that come to visit.