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

https://hectoruwog494.image-perth.org/why-do-some-single-ply-roofs-fail-in-the-first-10-years

Single ply roof guarantees usually cover 15-20 years, but the actual service life can stretch to 25-40 years if looked after properly. That’s because guarantees focus on material faults, not wear and tear or maintenance issues