I don't have a good answer. But, if you can access the top of the valve, you might try spraying silicone lube into the valve.

Unfortunately, some of the things people use on O-rings damage them -- Vaseline comes to mind; motor oil will also damage some types of elastomer. Unlike PVC, many O-rings are NOT very chemically resistant, and if you lubed with the wrong material, you may have created the very problem you wished to avoid.