Servo burnout rate - is this normal?

Got a Hexy up and running yesterday evening (Vine proof: vine.co/v/MiIKE7JYWHL), and have maybe 30-60 minutes total running time, but I’ve already lost a toe servo (pretty much immediately) and a calf servo to gear stripping.

This seems like a pretty high failure rate. Is it typical for the first few hours of operation? Or am I doing something wrong?

I’m running it with a 5-pack of 1.2V NiMHs for the servos (4 didn’t seem to be cutting it) and a 9V for the brain. Controlling over Bluetooth from OS X, updated Servotor to latest firmware.

(On the plus side my day started with my toddler running into the bedroom and shouting “Daddy your robot is really cool!” so it has the no-filter seal of approval…)