As I did with Fallout 3, I gave NV a solid but certainly not exhaustive playthrough right after release. And, seeing as it worked for F3, I'll probably wait till the GOTY edition comes out, buy that, scour the internet for the best mods, and wait till I have a reasonably free schedule to give it an exhaustive playthrough, usually with a more specific RP goal throughout opposed to my first playthrough's style (good vs evil, male vs female, dealing vs dealing death). Seeing as NV took well over 30 hours without actively seeking out sidequests, but doing most quests that my path took me across, I'd imagine it'll be a 100+ hour adventure with DLC, mods, and scouring the wastes. Sounds like a good Christmas.