Is there an electronic pre-treatment spray for long life reliability in connectors?
The following article may help you with some of the fundamentals you are looking into: A Perspective on Connector Reliability.  A connector will always introduce some type of resistance and it will possibly fail over time.  But there is a grease you could try to use for your connectors.  NO-OX-ID is the product that appeared to be effective for corrosion, copper deposit, rust, and general connector defects.