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

https://weekly-wiki.win/index.php/What_Questions_Should_I_Ask_Before_Signing_a_Single_Ply_Roof_Contract%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