What kind of blades are you using? Stock e-flight? I've had problems with bad warped blades where my heli only had about 3-4 minutes of flight.
test your blades for me.
Eat2muchrice’s Warped blade test
http://youtube.com/watch?v=_7PwNTXOWMs
Eat2muchrice’s Blade boil fix
http://youtube.com/watch?v=RmNv8OlG6GQ