What contact cleaner do you recommend?

I began by using Caig products (pro gold and deoxit) After reading about how these products degrade over time I stopped. I then read up on a product call Kontak and have been using it since. I stopped using the silver pastes because of their degrading over time as well.

be careful what chemicals you use, as some may affect the frequency response, after you have removed the oxides and other contaminants.

Kontak. Clean and dry has been working for me.

Save your money and by that new piece of music you have wanted.

Not to say that you will not convince yourself that you hear a difference. Just plug in and out several times every six months if you must. If your connectors fit snug and are of good quality you will have no issues. Is your system in a room with high humidity,(over 55%)?