Typically the tempertature variations pull is external aie into enclosures. This air condensates salts on the surfaces of enclosures.
The primary purposes of the grease are to keep out moisture, and prevent corrosion. Prevention of corrosion keeps the metal-to-metal contact point in a connector conducting electricity. I would try a moderate amount of silicone dielectric grease for coating terminals, like Locktite or Permatex.
Overfilling with grease can cause heat build up in some cases.