Don't forget to wash it with a recommended detergent (Nikwax makes one) before treating. Rinse twice. Dirt and detergent residue can be part of the issue.
I just did a couple pairs of ski pants and they seem to be doing well.
"Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." - Mark Twain