The other trick to these packs is that you can not tell the condition of a partially discharged pack. When you start out with one of these packs, you have to fly a few 'normal' flights, then top off the pack. By looking at how much charge went back into the pack, and dividing by the number of flights you just flew, you'll get an idea of how much charge you use per flight. Then you will be able to safely determine how many flights you feel comfortable with on a charge.

My big reason for wanting to switch to these packs is the rapid recharge time, but the long shelf life is a huge bonus.