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

https://tessatopmaid.com/approved-contractor-schemes-do-they-actually-matter-for-guarantees/

Single ply roof guarantees often promise 15-20 years, but the real service life can stretch to 25-40 years if looked after properly. These guarantees cover material defects, not wear and tear from weather or poor maintenance