My boat is a 2001 with original through-hulls made of mushroom fittings capped by ball valves (bronze). They generally look sound and function well after 10 years. My concern is electrolysis, as I've heard stories about fittings that look good but failed suddenly.

I haven't yet scraped off any bottom paint to see if they're pink on the outside metal. If they're pink I'll definitely replace, but otherwise I'm not sure... and would probably leave them alone.

I'd like to hear other people's opinions. Are thru-hulls like standing rigging that (experts say) should be replaced on a 10 year schedule?