Cleeds is right. Why put a dielectric on contact points? If you're worried about your connectors, clean them. There's several products on the market designed to do just that.
Dielectric grease on connection ends
I was changing a coil on one of my bikes earlier, and as always, applied a light film of dielectric grease on the coil outputs, and on the spark plug boots. A thought occurred to me that this may be a valid application in audio connections as well. A small amount applied with a cotton swab to bananas/spades/rca's etc. may help, and I'm thinking about giving it a go. Was wondering if this has been tried by any other members, and thoughts on the pro/con aspects.