Single ply roof guarantees, typically 15-20 years, cover defects but not the...

https://knoxuqsk688.cavandoragh.org/what-should-a-roof-survey-focus-on-for-an-older-single-ply-membrane

Single ply roof guarantees, typically 15-20 years, cover defects but not the full life the roof can deliver, which often stretches to 25-40 years with good care