Originally Posted by snubbyfan

The thing that makes a leather holster stiff is called collagen.
When a holster is wet molded the collagen is softened either by using hot water, placing the leather in an oven on a low setting, using a hair dryer, etc.
Heating and molding multiple times breaks down the collagen and dries the leather.
With time and use the collagen fibers break down and can never be reformed.
The only real way to reharden a holster that's gone all soft is to replace it.