The picture is of a typical discharge curve for a NiCd battery over time. In this case, the time isn't important, but what IS important is the location of the "knee" of the curve which begins at about 4.6 volts. You do NOT want to be flying when this occurs because it discharges very quickly at that point. Discharge rate is dependent on the load placed on the pack - number of servos, flying style, and other factors, all play a role in the discharge time from full charge to the "time to recharge" time.

Under no circumstances would I fly a 4.8 volt 700 mah NiCd pack more than four flights.

I use Voltwatch2 on all my planes. It gives a visual indication of the LOADED condition of the battery pack. I check it before and after each flight. If it begins to flicker to the yellow, it's time to recharge. This is my down time when I sit back, and enjoy some RC conversation with my fellow pilots as the pack charges.

CGr.