I agree about game length but a big map doesnt need to mean a long game really, but usually it does, and it seems to be the case here. This is not a game i intend to finish to 100%, but i'll have fun anyways i'm sure. I've never finished BG2 either, but i've played it many times (probably around 6-7 times) to perhaps 70% completion..
I usually don't care too much about endings anyways, never played a game where the story grabbed me so much that i needed to see it. I get tired of games very easily, even if they are good.
I've played a lot of games that were worth finishing at least in part because of the story. Either you simply don't care much for stories, or you're playing the wrong games.
I rarely play a game past 50% completion and not finish it. If a game isn't worth finishing to me, I'm not going to invest that much time in it to begin with.