We have a mountain bike that came equipped with hydraulic disk brakes. They have been trouble since the beginning and as a result she won't even ride it any more.

The brakes bind. It is almost as if you are putting on the brakes but there is no lever action involved.

Last time this happened I made some adjustments and they worked well. A month later, when she got around to riding, they were binding up again.

Is it normal to have to adjust the pads before riding or to do so monthly?

What causes this repetitious binding and how do I remedy it? Is this a moisture/contaminated fluid problem?

Are cable-actuated disks better in this regard? It is only occasionally ridden on streets (no off road riding).

My cars and motorcycles have hydraulic brakes but have never had this problem.

Bike is an otherwise nice TREK, brakes are Promax.