Green Energy

Well yes and no. It's a giant piece of silicon, but it's also exposed to high energy rays all the time. Panels can suffer from water ingress and then crack when it freezes. They are exposed to all sorts of animals, both big and small that can cause damage. Have their top surfaces get more opaque due to normal erosion. Experience huge swings in temperature every day. Those things can either outright break the panel, or slowly make it less efficient. UV rays alone cause a degradation of around 1% every year. However modern more efficient compact panels suffer more from this than the older kind. So old panels might still be going strong, but give a modern panel the same amount of ageing and it might do a lot worse.