Single ply roof guarantees often cover 15-20 years, but the actual roof can...

https://www.yankee-bookmarkings.win/single-ply-roof-guarantees-usually-cover-15-20-years-but-the-actual-service

Single ply roof guarantees often cover 15-20 years, but the actual roof can last 25-40 years with proper care. The guarantee usually covers materials and workmanship, not wear and tear or maintenance issues