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

https://daisydustmaid.com/overlay-vs-full-replacement-for-a-single-ply-roof-when-does-overlay-make-sense/

Single ply roof guarantees usually cover 15-20 years, but the actual service life often runs between 25-40 years. That’s because guarantees focus on material defects, not wear and tear from daily weather or poor maintenance