Peggy, there is a statement I totally agree with... with the exception of a few things, it would seem that most everything we all come across isn't built like it was 20-30-40 years ago. You are right...."IF" you could get your hands on a gate valve, that was BRAND NEW...from 30 years ago, and install it, how long would it last....compared to the quality of today.... It is a shame things aren't the way they used to be.
Very interesting conversation. I tend to think parts can last a lot longer than many popular theories too - especially for those of us in fresh water with boats hauled out 6 months of the year for winter.
You can still get quality parts. I just replaced my gate valves with Groco flange adapters and in-line ball valves, and believe me, those things are build to withstand things my old gate valves never dreamed of. In 1977 there was no ABYC code requiring seacocks to withstand a 500 lb. impact, which may be part of the reason for the heavier material (just guessing).
I didn't really believe that my old gates were failing, or in immediate danger. Rather, the best reason to do the gate valve swap out came down to the changes in installation standards over the years. My boat had old plywood backing plates which were getting soft, and no bolts to secure the hull seal. I suspect many gate valves installations are similar to what I had. I now have 1/2" G10 backing plates bedded in thickened epoxy, and heavy through-bolts ensuring that the threads won't loosen up over time and the sealant won't be flexing more than necessary. Now that WILL make a difference, as I could spin one of my through hulls with a pipe wrench, and I had many places where I could see the sealant joint was failing.
By the time you do the work to update the installation standards, the additional cost of plumbing parts is truly small compared to your labor (or the price of a yard technician! Yikes!). I wouldn't do it just for the convenient handles, but I do appreciate that convenience. What I really appreciate is knowing that my new plumbing is not going to be compromised if a battery kicks loose and smacks it.