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

https://mike-wiki.win/index.php/What_Does_%22Whole-Life_Cost%22_Mean_for_Flat_Roofing_Decisions%3F

Single ply roof guarantees often cover 15-20 years, but the real service life can stretch 25-40 years with proper care. Think of the guarantee as a manufacturer’s promise if things go wrong early