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

https://wiki-cable.win/index.php/How_Do_Seams_Fail_on_Single_Ply_Roofs_Over_Time%3F

Single ply roof guarantees often cover 15-20 years, but the real service life can stretch 25-40 years if looked after properly. Guarantees focus on materials and workmanship, not wear and tear or how the roof’s used