Yeah, first time passes in all with BGS, and working f/t. Took me about 13 months start to finish, studied about 3-3.5 hours a night in the week pretty solidly (with the odd night off), and generally kept weekends free to spend entirely with girlfriend and socialise. Go out of my brain otherwise.
I slowed it down somewhat post 9/11 and Xmas, so it can certainly be done quicker than that, but as said, why rush. Do 'em when you feel ready (as you'll be anyway).
I would periodically pick a topic that I'd already covered some weeks back, and at least skim read it again, sometimes more thoroughly, just to "keep it a bit fresher" than waiting till I'd got to the end of the material before looking at the early stuff again, found that helped me a fair bit when it came to revision.
Brush ups are excellent at BGS, provided you've covered and understood the material prior to going down, or at least understood the vast majority of it, you can always clear up minor problem areas when you're down there, but they do go at a fair old pace on the brush ups.
Good luck.