Single ply roof guarantees typically 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 typically cover 15-20 years, but the actual service life can stretch up to 25-40 years if the roof is properly maintained. Guarantees focus on materials and installation, not wear from weather or blocked drains