First Time is the Toughest
One of the things I did to keep track of the three minute project was to mark intros and outtro frame numbers. It's something we'd do in radio when editing commercials, back in the days when editing was done with a razor blade and a splicing (V) block. Screw that up, and you might have to rerecord a whole show.
I still have to redo a whole presentation, but my intro and outtro numbers? They're calculations of how long my scenes are supposed to last. The first time around, it may have been the MOST time consuming part of the project. With them, it's taking a fraction of the time.