you dont need to suck the batt down untill the rotors will not turn.
as far as charging goes nmh batts take a few charges and discharges(cycles)before they hold what they say.
a 600mah batt charged at 600ma(.6a)would charge in apox 1 hour
1200ma(1.2a) would charge it in 30 mins
300ma(.3a) would do it in 2 hours

there is a charger,i beleive by hobbico,made to charge all of the fire bird batteries.it will charge ncd and nmh 5-7 cells i know,maybe 8,with a selectable charge rate from 200ma(.2a) to 1200ma(1.2a).works off of car ciggarette lighter socket.i got one at my local hobby shop for only $12.99. thats a whole lot of charger for not a whole lot of money.sounds perfect for your heli batt

notice there is a diff in mah and ma and a and ah