A well machined connection made from quality ss will probably last a lifetime. A crappy machined connection made of crappy metal, like some of the Chinese manufacturers use could last until you try to screw something into it a couple of times, all depends. It's a hard question to answer unless you want to shell out the money for known top quality
devices.
Noalox is usually only used for the
threads of the
mod body, some even frown upon it's use for 510 connections. From what I've read it could give off fumes from the heat that would then be inhaled. It's probably better to use a light coat of vaseline or even chapstick on the body. Noalox is'nt really designed to be a lubricant, it can harden up over time. The 510 threads really don't need anything. It would'nt hurt to put the ever so slightest bit of Noalox on the electrical connection points if they are a material that oxidizes quickly. That's my understanding at this point, but i'm no expert on electrical connections, or lubricants for that matter.