Gold-Titanium isn't anywhere near as strong as the films make it out to be. If that's all the suits where made of, they'd shatter on some of the impacts he takes, bullets would do more damage than we've seen and he'd certainly never survive more than one outing in full combat.
So I assume there are other metals and the Ag/Ti alloy is the base metal that makes up 60% or more.
But based on the materials we know he uses, the suits are more ablative in nature, designed to use many plates that spread out damage and are replaced when needed.
The interior endoskeletal frames probably last much longer and take less damage.