1) Keep wiper bands free of any dirt with lighter fluid! Lubricate wiper bands with a very small amount of thin braid juice or WD40 and wipe off excess with a paper towel. Never use sandpaper on PCB!
2) Your Difalco controller has ball bearings on the trigger pivot. While the ball bearings will never wear out the hole in the nylon trigger may compress or wear over time. This will induce play in the trigger and possible cause loss of wiper button tension. If you push sideways where the wiper arm meets the trigger and feel side play you can ever so gently adjust the pivot nut until the side play is zero.
3) Maintain the best possible braking by keeping the brass trigger contact on the trigger and the brass brake screw areas bright and shiny. Use an emery board or sandpaper to clean any black arcing from these areas.