Not long, (10-15 minutes max) I have a friend who just got the AR Drone 2.0 and I was shocked when I saw what it could do. But, getting a heavy Contour or Go pro on one is over the weight limit...
You can get high end ones (around $700 that will hold cameras and such, but they cost so much...)
Certainly made my wheels start turning. I found an AR drone 1.o locally for $150.