I'm still using the sparse remnants of my first grizzly rooster cape purchased by me from Blue Ribbon Flies back in 1984. Still as 'supple' as when purchased although there is not much left to work with. My opinion, after 26 years of tying is, as long as you keep the bugs out, feathers seem to keep very well.
Kelly
Tight Lines,
Kelly.
"There will be days when the fishing is better than one's most optimistic forecast, others when it is far worse. Either is a gain over just staying home."
Roderick Haig-Brown, "Fisherman's Spring"