Single ply roof guarantees often last 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 last 15-20 years, but the real service life can stretch to 25-40 years with proper care. Guarantees cover materials and installation but don’t account for wear and tear or weather