I think the reason I don't like the ones that occur in the middle of a game is that due to having been cash constrained in the past, I didn't want to spend more money than the basic game in case I didn't like it. So I'd play the game, usually through, then if I liked it go buy the expansion pack, but to enjoy the expansion, either I'd have to reload an old game and replay from that point, or just replay the whole game. For something like BG (which I think I played through 3 times back to back!), not a problem, but for a lot of other games, I wouldn't want to invest them time. I'd be willing to say put another 5-10 hours in to play the expansion, but not that 5-10 plus another 20+ for the OC.