Single ply roof guarantees often cover 15-20 years, reflecting manufacturer...

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

Single ply roof guarantees often cover 15-20 years, reflecting manufacturer confidence in their product’s performance under ideal conditions. But with good care, these roofs can last 25-40 years