There were lots of debates and reports in Yachting Monthly a few years ago about defective seacocks and how to identify reliable ones. Among their recommendations they also suggested it could be interesting to look at “plastic” ones, which are not cheaper but should last forever.
I replaced mine with Vetus metal ones four years ago (my N33 is a 1981 model), except the one of the seawater intake, which had been replaced earlier. But I noticed that the handle was rusty and about to break, so I had a new inox one made and fitted by my boatyard. I noticed many times that the handles supplied with seacocks were of poor quality and get oxyded earlier than the seacocks themselves.
Hope this helps,