Single ply roof guarantees often promise 15-20 years, but the real service life...

https://golf-wiki.win/index.php/Why_Is_My_Single_Ply_Roof_Guarantee_Only_15_Years_If_People_Say_40%3F

Single ply roof guarantees often promise 15-20 years, but the real service life can stretch to 25-40 years with proper care. The guarantee covers product defects, not wear and tear or poor maintenance