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

https://cristiansbrilliantblog.fotosdefrases.com/ponding-water-at-upstands-design-problem-or-maintenance-issue

Single ply roof guarantees usually cover 15-20 years, but the actual service life can stretch to 25-40 years with proper care. That’s because guarantees focus on manufacturing defects, not wear and tear or poor installation