Single ply roof guarantees, usually 15-20 years, cover workmanship and material...

https://www.cast-bookmarks.win/single-ply-roof-guarantees-typically-last-15-20-years-but-the-roof-itself-can

Single ply roof guarantees, usually 15-20 years, cover workmanship and material faults but don’t reflect the full service life, which can be 25-40 years with proper care. Think of the guarantee as a safety net, not the roof’s lifespan