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

https://wiki-nest.win/index.php/Is_It_Normal_for_a_Roof_to_Blister_if_the_Design_Is_Wrong%3F

Single ply roof guarantees often cover 15-20 years, but the actual service life can stretch to 25-40 years with proper care. These warranties focus on materials, not wear and tear or maintenance