Like most people you probably use the driver window a lot more. I used to use a silicon spray on my xterra windows channels to keep them lubed. Not sure if its recommended for the Focus I cant see why not.
Rain X in the outside of the side windows really saves the power window motors.
With the window dry and sticky the motor is stressed.
Also if any tree sap gets INTO the weather strip in the door which the window rubs against.... tree sap can really burn out a window motor.
I usually spray some silicone right into the furry stuff of the door window edge weather strip with the window down, just to alleviate any chance stuff like tree sap is on the weather strip.
Even ONE TIME parked under a tree dripping tiny bits of sap can really do in the window as far as struggling to open or close and burning out the motor, even months later if the sap is on the weather strip the window rubs against....
Same here, but at one point, my front passenger window would roll up very slowly and it sounded as if it were straining to roll up. I brought it to the dealer's attention and they lubricated something in there which mitigated the problem.