With a much larger gasket holding the lid on my boiler with a different machine, I used a torque wrench and found that after the first couple of weeks, the hold loosened a bit, so i retightened. After a couple of months the torque had loosened and I tightened again. But you've got people on here who are much more expert restorers than me who haven't mentioned that, so let's see what they say.

I'd keep an eye on it and tighten it if needed. Depends on the metal, I think. Some metals flex more under pressure and need to be checked for bolt tightness in the beginning. My experience with alloy car tire rim lug nuts is they need to be checked after short distance and retightened to be sure they're secure. I do it atleast 3 times. If you don't know what was done at the factory torque or thread sealant wise to secure the part it wouldn't hurt checking it every now and again I think.

Stainless on brass or copper corrosion could be a galvanic reaction. Grease would treat that. Anytime there's dissimilar metals coming into contact it's good practice to wrap the threads in teflon and dielectric grease them up. I've used Molykote Dow 111 grease on connections and threads. I also use teflon tape and thread sealant paste on water connections.