Mine are all dimmable, but no I've never changed the settings. Honestly... I'm scared, and they work great, so why shake the cage?
I take that back ... I ran two of them at 750 watts for 1 day once. I thought they were starting to burn a section, but the distance was fine so I added some Magnezium and turned the lights back up the next day. I would never change the settings while the bulb is lit. Other than that, always at 1000 watts.