I've been doing the longevity meditation for a week or two now, at different times of the day, and at some point during the hour(or a few points), I nod off. Does this mean that I've got to make up the 'lost time'?
Thanks.

I don't think you have to make up any "time" just continue on where you left off. I have found that when this has happened to me when I "wake up" I am actually still sweeping and breathing. It is more like I went into an altered state rather than simply dozed off.

Enjoy.