Feathers will soften up after shooting them several months, and be even quieter, but the 'velcro effect' never wears out.

If the feathers get too ruffled or smashed so far out of shape you can't straighten them up by hand, you can definitely refresh them and get them perfectly lined out again by running them thru steam. I like to fire up the wife's teapot and use the pressurized steam coming out of the spout.

Sorry, but I can't say how long the waterproofing agents work. I never have used them. Started off using the cheapest hairspray I could find to keep my feathers in shape in the rain. Then I got the bright idea of spraying them with Scotchguard. It works, so I never used the 'real' stuff.

Scotchguard has given me a good 8 hours of dry feathers on foggy, drizzly days. I always carry a gallon size freezer bag to cover my feathers in a frog strangling downpour.