On nickel cadmium batteries you should always store them fully charged, once you have used them for
a flying session or just checking out the controls of the airplane they should be charged. I also put them
on charge again the night before I go out the flying to make sure they are fully charged. The 600mah that
you have should give you about 45 to 60 minutes of actual flying time provided that the servos are not under
a heavy load, like from a stalled servo or a servo that is binding. When you are checking out the flight controls
if you hear a servo buzzing slightly, that is an indication that it may be under a slight load or binding in the control
surfaces. Binding will drain a battery very quickly. You may also want to invest in a higher "mah" battery and also
go with a nickel metal hydride "NiMH" type of battery. Check out your local hobby shop for different ones.

Bill D.