The actual usage per flight will depend on quite a few factors including your flying style, the particular airplane and how big the control surfaces are, the servos used, etc. just to mention a few factors. Your airplane may use more or less power than similar ones of the same type. You'll have to determine the exact power used per flight by recharging the batteries then dividing by the number of flights. That will tell you the power used by your airplane and that's what counts .... not what someone else's plane uses.