Originally posted by DnvrFox
It also takes energy to keep it at a constant speed, due to resistance of air and the pull of gravity.
For air resistance, yes. For gravity, only if you're going uphill. But when going uphill, assuming you are not accelerating to a faster speed, the rotational speed of the wheels do not change, so the only factor is total system mass. So, whether you have an extra pound on the wheels, in the frame, or around your middle, the force required of you to lift that while climbing is the same.
Dave