I run serperate receiver and ignition batteries on my model and get almost identical run down between the batteries; roughly 100mah per battery per flight. Ignition is slightly less and receiver is slightly more. The batteries are two 1,100Mah LiFe batteries which easily allows for 6 flights + a nice safety barrier.

BTW I got my packs from http://www.hangtimes.com/ after some communication with them I was able to get a battery that allows for both charging and balancing through one regular futaba DSC port on the side of the model, very easy for rapid field charging as I don't have to take off the wing to get at a balancer connector. Might be useful for someone...