Im known for over tightening things. Everything from pop bottles to nuts and bolts. Its something I have to be careful of. Its a natural habit for me to make sure things are snug.
When you overtighten things, as with metal fasteners, you are creating stresses and strains. You are squishing the threads together. Eventually the metal will tear a little bit and start to gall up and tear in the thread. This makes it harder and harder to turn till eventually it siezes up.
If you have the same issue as I do and even if you dont, I recommend putting some anti-sieze compound of some type on your lid clamp down threads of your pressure pot. I use a nickel based antisieze. There are lots out there all of them just as good as the other. You have metal turning against metal. You wouldnt run your engine without motor oil. This is exactly the same. They sieze. Just the results of not using anti sieze are alot less traumatic and costly than running a motor without oil.
You'll be extending the life of your pressure pot substantially.