Single ply roof guarantees, usually 15-20 years, cover product defects but...

https://sirachapete736.gumroad.com/p/what-would-stop-a-single-ply-roof-reaching-35-years

Single ply roof guarantees, usually 15-20 years, cover product defects but don’t always reflect the roof’s full service life, which can reach 25-40 years with good care. To help your roof last longer, get annual inspections by an SPRA-approved contractor