Two failure modes.
1. Blow out a seal (lower springs help induce this). Evidenced by oil ont he wheel & strut.
2. Internal seal failure. Doesn't damp. Evidenced by 'cupping' on your expensive tires. (D'oh!)
So don't 'assume' they are fine. You can't just 'bounce check' them like shock absorbers.
You are right - a stock set up should (I expect) to get 60K MAX out the struts.