Single ply roof guarantees usually cover 15-20 years, but the actual roof can...

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

Single ply roof guarantees usually cover 15-20 years, but the actual roof can last 25-40 years with good care. Guarantees often focus on materials, not wear and tear or damage from poor maintenance