My problem with wet holsters, has almost always been from sweat. I sweat like a pig, work and play outdoors, year round, and it gets steamy here in the summers. Prior to kydex, I tried everything I could think of to stop the sweat from soaking the holster, and gun. At the end of using them, I was rotating through two Galco Royal Guards in the summer, and usually replacing one each year.
Even with the rotation, once both were wet, I was just swapping a slightly less wet one for a soaked one each day. They never dried out as long as I was sweating and the gun was always in a wet and caustic environment, quickly causing rust.
This was the last Royal Guard I was using before switching to a Blade Tech kydex IWB. This was after about a month of use in the summer. The duct tape on the back was an attempt at slowing sweat from soaking the holster. It didnt work.
When the pic was taken, the holster had been sitting in a box for about 10 years, and was sold soon after.
This is the Blade Tech after over 10 years of daily use (on the right). The other holster was a second spare that was new and unused. As you can see, at some point, I broke the tip of the sweat guard off, but it was still completely functional. I also replaced the straps a couple of times over its time in use.
Besides considerably reducing the rust issue, the cost savings factor was also considerable. I went from $75 a year, to $55 for over 10 years. I still have the holster too, and its as functional today, as it was when I first bought it, and put it away, over 10 years later.