If it's not doing the crazy bubbling thing, I wouldn't. Sometimes that type of valve won't shut all the way again because they hardly ever get moved. I've only done it because it was the only way to keep the water heater working and there was no loss if it didn't work.

It's worked the 3 times I've done it on 3 different water heaters but I'd hate for you to do it unless it's a last ditch effort. All three of those made that distinctive boiling noise. You know it when you hear it. It really stands out as weird.