Hard-to-crank manual windows

[mirapatec]

The manual-crank windows on my 2012 Yaris are becoming extremely difficult to roll up and down. The driver's window has gotten to the point where I am afraid I am going to rip the window crank knob off. Seriously.

As a test, I sprayed a small amount of WD-40 into the side channels, and the window immediately became much easier to roll up and down. This lasted about a week before they became difficult again. I am concerned that continued use of WD-40 is not the appropriate procedure for this issue.

Has anyone else suffered with this condition? Is there anything that can be done at home instead of making an appointment at the dealership?