A photovoltaics system should have a life of at least 20 years to be eligible for the statutory electricity feed compensation. You can generally expect a useful life of 30 to 40 years.
Module manufacturers basically offer a 25 year warranty at an efficiency loss of no more than 20%.
The support structure (= gehrtec Base or Top, see products) of the modules is made of aluminium or stainless steel and has a very high useful life. This also applies to the UV resistant special cables (gehrtec Nubbel).