Someday I will learn how to replace these things and put in some better quality equipment...
Replace them with 1/4 valves when you do.
If they're threaded connections, most people that can "turn a wrench" could replace them. Obviously remember to turn off the water supply (you'll still get some "spillage" but nothing you can't clean up with a towel), use sealing tape (on metal pipe), and crank them down very firm.