I too warrant my work (officially) for a year. It has never come up, but if someone were to call me and let me know there was a problem that they felt was related to installer error I would probably investigate and very likely take care of the problem for free. I do hire people to help me from time to time, and I don't always see their work every step of the way. I live in a pretty small community now too, so many of my customers are friends and friends of friends. It pays to take care of issues even if its past the official warranty period.