The power wire that runs between the factory headlamp harness and the ballast is the ideal place to cut the power wire and install a switch for the headlight. This will allow to turn off the headlight during startup.
What is killing the ballast is when the ignition is turned on, the headlight is powered on, then you start the bike, while starting the bike the headlight goes off, the once the bike is running the headlight comes back on. This is called a rapid fire scenario.
Ideally you want the hid to come on and stabilize. This is when the light comes on and reaches the optimum brightness. Usually 30-60 seconds
While turning on and off the hid so quickly not allowing for the stabilization period to occur this is what is killing the bulbs and ballasts.
Solution. Switch would be ideal. Have the hid off during start up, let bike warm up, then turn on headlight. Then the headlight is only turning on once and allows for stabilization.
BB