i think the amp doesen't matter. . . . only the voltage. . . . the more amp. . the longer playtime. . .

but your esc has to have a Lipo- Low voltage cut-off which i think it doesn't have
this feature lengthens your lipo's life. It prevents it from dropping voltage to lower than 6v

see specs:
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAUPU
you can get a NOVAK SMART STOP lipo cut off, or just get a lowvoltage buzzer