I'm not one of those, let me rush through the MQ and the game type guys. I'm the type of guy who spends 90% of his time looking through empty containers. Looking at absolutely everything even when it yields no loot.
Depends on how you play.
For me, I've beaten it 4 times, 5 if you want to consider that my current one is level 30 and on its way to helping NCR. I do a lot of looting and such, yes, but I think the reason why it seemed like I rushed through them, they all have about 50 hours on each if you want to call that "rushing", I just work too efficiently, even with my first character. Perhaps what I need is changing the amount of XP that I need in order to gain a level... that'll keep me playing for a bit longer as I can't stand not having a character at max level when I finish with it.