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

https://wiki-tonic.win/index.php/What_Parts_of_a_Membrane_Roof_Usually_Fail_First%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