Single ply roof guarantees usually last 15-20 years, but the roof itself can...

https://trevorsinspiringnews.yousher.com/how-long-should-a-quality-membrane-roof-last-on-a-distribution-centre

Single ply roof guarantees usually last 15-20 years, but the roof itself can often serve 25-40 years if looked after properly. Guarantees cover specific faults, not general wear and tear over time