Don't buy normal trousers belts, instead buy elastic belts which can last literally for life
(i5.walmartimages.com)
Though leather belts stretch over time, the only belt I ever had that actually broke did so after more than a decade of heavy use when the metal buckle eventually gave in.
I have a textile hiking belt (Fjellräven) that I am not particularly happy with. It doesn't really stay firm over time when walking for hours and hours, and adjusting it underneath the backpack is a pain. An elastic belt with a normal buckle would probably have been better.