Single ply roof guarantees, often 15-20 years, cover materials and workmanship...

https://astro-wiki.win/index.php/How_Long_Should_a_Quality_Membrane_Roof_Last_on_a_Distribution_Centre%3F

Single ply roof guarantees, often 15-20 years, cover materials and workmanship but don’t always reflect the full lifespan, which can stretch 25-40 years with proper care