Single ply roof guarantees, often 15-20 years, cover workmanship and materials...

https://www.paste-bookmarks.win/single-ply-roof-guarantees-usually-last-15-20-years-but-the-real-service-life

Single ply roof guarantees, often 15-20 years, cover workmanship and materials but don’t always reflect the roof’s full service life, which can stretch to 25-40 years with proper care