See, I think the difference between a collector/hoarder and one that just happens to have a lot of paraphernelia is that the latter is, even though some might have been "collected" because of certain rare qualities, is ready to use the paraphernelia.
This sparked from a remark on Facebook from renowned fly tyer Gunnar Brammer, who recently posted a fantastic looking BEAST-fly (a Bob Popovics-creation) for which he had used some bucktail he'd been saving. I commented on the hoarding aspect, because I've been there, but years ago I came to realise the stupidity of it. Spending prime money on prime materials that never gets used...
That doesn't mean you shouldn't think. Don't use your best, longest bucktail for a 2-inch fly. Just choose the material wisely, and then save the long stuff for the long flies. But of course, with natural materials there is always the aspect of quality. If you happen upon a certain dry fly neck, a batch of prime quality bucktail and you use a lot, a superior game skin etc., just get it if you can afford it.
But don't let it sit - use it, for Heaven's sake. A few years ago I found a grade 1 Whiting dry fly neck, in dark dun colour, and I think I bought it over 10 years ago and I've never plucked a feather. And that's when I realised how stupid that is. I have a thing for natural game brown/red cock necks, and I think I have 10 of them, maybe more. But rather than letting the best one stay in the bottom of the box, I now use it.
And naturals is one thing - sometimes I'll even do it with synthetics. If I stumble over something, say a perfect fiber for tying sand eels, I'll stock up, and stock up good. You never know when these materials suddenly go out of production or become hard to get for some some reason. But I don't let them sit and use the second best, nope. I use them and if I happen to use them up, unable to get more, I'll just use the second best. And search for the best in the meantime :-).
The PoD is a section of the book shelf behind my desk, roughly half of it. It's floor to ceiling with boxes and boxes of materials. Believe me or not, it wasn't always this organised, but when you get enough of it and things become hard (and quickly impossible, believe me) to find, and some organisation is needed.
Have a great weekend!