Just as an aside for those of you working on the power window regulator
problems.  One of mine stopped dead cold (fortunately full up).  I took
everything out and was just about to order a replacement motor.  When I
checked it out of the car, it budged just a bit.  Of course, being frugle,
an idea popped up.

I disassebled the motor (two screws if I remember correctly) and took it
apart.  Found that the lubricant on the shaft had soldified in a gummy mass,
which was binding the motor.  Cleaned the shaft with emery, relubed with
white lith grease (not too much) and reassembled.  Low and behold, it worked
like a charm.

So.. if your power windows are gradually slowing down, you may be able to
salvage the motor by doing the same.