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

https://knoxuqsk688.cavandoragh.org/do-certified-installers-really-make-a-roof-last-longer

Single ply roof guarantees usually run 15-20 years, but the actual service life can stretch to 25-40 years if the roof’s looked after properly. The guarantee covers manufacturing flaws, not wear and tear or poor upkeep