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

https://wiki-coast.win/index.php/What_is_SPRA_and_Should_I_Pick_a_SPRA_Contractor%3F

Single ply roof guarantees typically cover 15-20 years, but the real service life can stretch to 25-40 years with proper care. The guarantee mainly protects against material faults, not wear and tear or damage from poor maintenance