wbeaton....same here, I always use it on my trailer 4 wire connectors. I am pretty sure that plug wire kits used to come with a little tube of dielectric grease, but it's been a while since I put new wires on....I usually recycle/clean up old ones.
Figured dielectric grease couldn't hurt, just wanted to throw it out there.
I use it on my snow plow harness connections, my trailer plug and a few other places I'd rather not speak about in public. It can't hurt the plug wires I don't think. But I'd clean it out from time to time and replace since grease attracts dirt and water.