[user104658]

I couldn't get into NV at all for some reason, I think the most I ever played was was about 4 hours (though I tried to start several times).

My longest (and last) play-through of Fallout 3 lasted something like 3 months and included every piece of DLC and a load of playing around with mods, plus I;d played it start to finish twice before that.

I can't actually pinpoint exactly why I wasn't gripped by NV, though. Similar happened with TES - I played Morrowind to death, couldn't get into Oblivion at all, but then loved Skyrim.