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

https://riveraeku966.almoheet-travel.com/how-do-i-explain-to-my-boss-why-a-15-year-guarantee-is-not-the-lifespan

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 material faults, not wear and tear or poor maintenance