Single ply roof guarantees, usually 15-20 years, cover defects but don’t always...

https://wiki-club.win/index.php/What_Would_Stop_a_Single_Ply_Roof_Reaching_35_Years%3F

Single ply roof guarantees, usually 15-20 years, cover defects but don’t always reflect the roof’s full lifespan, which can be 25-40 years with proper care. To help your roof reach its potential, arrange annual inspections and clear drains regularly