Exterior woodwork can look beautiful for a very long time with regular maintenance. Everybody gets a little spring fever, and for a lot of us, that means cleaning. Some folks, myself included, like a bit of cleanup in the fall as well. Either way, if you make inspection of your exterior part of your Spring/Fall routine, you might spot some problems that can lead to costly replacement later.
Flaking paint is a sure indication of a problem.
Gaps in caulk joints are an entry place for water.
If you suspect rot, stick a blade or an awl in the problem area. If the blade sinks deeper than 1/4″, the wood is badly damaged. If not, repairs can be made.