Single ply roof guarantees usually cover 15-20 years, but the actual service...

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

Single ply roof guarantees usually cover 15-20 years, but the actual service life can stretch to 25-40 years with proper care. Guarantees focus on materials and workmanship, not wear and tear or maintenance issues