Mike Hartigan writes:

Any suggestions on where to buy valves that will outlast the fixture
that they are feeding?

I have the same problem. The brass bodies are corroded away internally
after 10 or 20 years. The "Brass Craft" brand sold and Home Depot seems to
be the same stuff.

My solution is to solder on 1/2" male pipe thread adapters to the 1/2"
copper stubs, and use a new 1/4-turn valve with female pipe threads. At
least that way they are easy to replace, and the soldering part is easier
than soldering on a valve. And the 1/4-turn valves (still made by the same
outfit) seem like they might live longer.