I put ArmorAll on my chest waders every spring after the completion of the waterfowl hunting season (although this year I have not done this, just lack of dilligence on my part). I had received some guidance to do this to extend the life of my waders, probably on a hunting site such as this. I can't really testify to the effectiveness of this procedure: my waders are only three maybe four years old and they haven't started leaking yet. Maybe the true test would be a side-by-side comparison of the same brand of waders -- one treated annually with ArmorAll one not treated, both used equally in waterfowling.
I also think keeping them out of the sun and hanging them up probably contributes to the waders lasting longer.