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

https://www.bookmark-step.win/single-ply-roof-guarantees-often-cover-15-20-years-but-in-reality-these-roofs

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years if looked after properly. Guarantees focus on materials and workmanship, not wear and tear or damage over time