How often do you tighten your valve covers and how much?

I use a very vintage (late 40s early 50s) Snap On FAR70B. Some incorrectly call it an air ratchet, but it's not. It's a nut runner made for low torque, high speed assembly line work for such things as tin on engines. It only goes about 5-8 foot pounds, but it gets there in a HURRY. I had a close family friend who was a Snap On dealer just lay it in my hand one day and he said "don't say I never gave you anything" and I've been using the hound out of it ever since. He even gave me a new replacement head for it, which I've never needed to install. It still runs like a new one.