A hot air balloon requires a great deal of fuel to keep it aloft, so that you can't fly it even for one day. A gas balloon, which usually uses helium, has the problem that the helium cools at night when the sun is not on it, and you have to throw ballast overboard to keep it from going to the surface.

Chasing the Wind: The Autobiography of Steve Fossett (ed. Virgin Books, 2006)