I've replaced two so far and I have a 3rd that is on its way out.
I had not previously tried any cleaning. My car is garaged day and night, and never driven in snow, so I dont have any sort of corrosion problems. Cleaning hadnt crossed my mind.
Seems like the price on new modules is coming down, so while the idea of rebuilding them is great, I don't know if you could price it lto make it profitable for yourself but yet be priced lower than a brand new one.