I keep the boxes etc. for MP and larger Encore stuff, mostly because they make good, safe storage, and flatten and keep the rest. Plastic bubbles etc. get put into recycling.
That said, I mostly buy loose anyway, and so far I haven't bought anything 'vintage'.

I'm not planning on selling off my own collection if I can avoid it, and for me it's very much about the toys rather than the packaging.

@Burn - I'd try and offload them, either for payment or even for free with the cost of postage and mail packaging covered. If someone else wants them and you don't then it seems better to me to not put them to waste.