From my limited experience (two Terranos over 6 yrs) I think that the window motors are only just powerful enough to cope providing the sliders are kept well lubricated with slippery silicon.
Whenever I have had window or sunroof malfunctions I have always been able to cure them by the following crude process-----
Liberaly squirting silicon fluid down the runners,
Start the engine with a few extra revs to get electrical system volts at optimum
Use a device ( sink plunger etc) to vacuum onto glass
Use the above device to assist the poor little motor to get things moving
Seems that lack of use is the culprit 'cos after a good old workout all windows "free up " and work well
Does it for me anyway