I get 3-5 years out of a pair of lacrosse La Granges. The only thing I do is store them in a natural position without creasing them.
I see no reason to "treat" the pair I prefer with anything. They are durable, functional, and cheap enough that I could afford to replace them annually if I had to. 1x every 3-5 years is a hell of a bargain as far as I'm concerned.