My 10 year guarantee is simple and to the point. If any paint that I apply lifts, peels, bubbles, or detaches form any surface for any reason within 10 years from the time that I painted that area, then I will scrape, prime, and repaint that area at absolutely no charge to the home owner.
I started offering an 8 year guarantee back around 1980 and a few years ago I decided to change it to a 10 year guarantee. There are two reasons I offer this guarantee. One is because most of my competition does not offer any kind of guarantee, and two, because it gets me more work! If I am called back say after 9 years to touch up a fascia board that is starting to peel, it is going to take me about an hour to fix it. But for that one hour of work, I know that homeowner is going to be impressed and chances are they are going to get my bid when the house is ready to be painted again. Not only that, but they are probably going to tell friends and neighbors about me coming back after 9 years and honoring my guarantee, which is going to lead to more work. So not only do I honor my guarantee, I welcome the opportunity to do so.