Many people wonder how long PV modules will last. Most people with an opinion are just guessing. I actually have some experience in this arena, however, since my oldest PV module is now 30 years old. I recently ran some electrical tests on the old PV module. If you're interested in the results, click the link:  http://www.greenbuildingadvisor.com/blogs/dept/musings/testing-thirty-year-old-photovoltaic-module