Two tips:
1) get a tap and die set. Repair threads instead of chucking whole assemblies.
2) on pans, VCGs, etc., try to do this: a) tighten to spec, let sit overnight. B) Retighten. You will be surprised how often the material takes a set and loosens the fit. c) run to operating temp, let fully cool, repeat again.
This will result in a very long lived seal.