Couldn't hurt. Whether its necessary is entirely dependent on your setup and burner. I don't need one for my ball valves but I fabricated a heat shield for my sight glass on my boil keggle. I trimmed an old motorcycle license plate and attached a conduit hanger to it. Snaps right in place.
I don't on the ball valve. But it depends on how close your valve is in relation to flame. I do use one on the dip tube/thermometer to keep it from overheating. Regardless, it definitely isn't going to hurt anything.
Next time you boil, place your hand where your ball valve is. If it feels hot enough for the rubber handle to melt, I suppose you might need a heat shield.