I've been flying without a camera mounted for the past few days just to maximize my practice time and I was really surprised at the extended time I get. I haven't kept track of the exact minutes but it is substantial.
Probably because I've been using a heavier GoPro2 with it's full housing (which I'm glad I used. I had the whole camera mount break off 50 feet over pavement, no harm done. I think it would have been trashed if it was only in the DJI GoPro housing). My MicroSD came today for my GoPro 3, so that should lighten the load once my replacement camera mount arrives.
Worth noting also (and probably stating the obvious) but the little thing is quite a bit quicker and more responsive without the camera. I was amazed at how quickly it did 180 turns. Instills more confidence flying when you know you can bring it to a stop instantly.