Wood rot seems to be a growing epidemic in homes and something we see a lot here at DogGoneHandy. Some of the rot can be traced to poor maintenance habits by homeowners, some to poor building practices by the trades and, believe it or not, some to the lumber companies.
If you want to prevent wood rot, you need to keep it dry. Wood rot is simply different fungi that are consuming the wood. The fungi need water to live. You keep wood dry by keeping it painted and sealed. It's also a great idea to keep it above horizontal masonry or concrete surfaces by at least 2 inches.