When I was a younger man, I was an avid scuba diver. I used a silicone based wax to lube the zippers on my wet suits. About a month ago I was reorganizing some of my material possessions and I came across a stick of this stuff . It was about 16 years old and still looked as good as the day I bought it. In addition to zippers, I discovered it worked great on drawer slides and sliding door tracks, even in extreme temperatures.
After a Google search, I couldn't find the exact brand I used, but today's equivalent seems to be Max Wax