I have a 1650 rx pack in a Tmaxx and it'll easily last 40min, it goes several hours between charges. This Tmaxx runs an upgraded strg servo and still lasts a long time even with teh added drain from a 175inoz servo.

For rx batts, I try to charge them at 0.5amps as a slow charge, when I've absolutely got to get it charged as fast as possible, I'll use 1amp.