Single ply roof guarantees typically cover 15-20 years, but the roof can...

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

Single ply roof guarantees typically cover 15-20 years, but the roof can actually last 25-40 years with proper care. The guarantee focuses on materials and workmanship, not long-term wear and tear