I'll fifth keeping them - not that I'll ever sell my VR-7s, BUT you never know. The crates were quite large and we had to take them apart just to get the speakers out, so we kept the crates in pieces, trying to clearly number sides for later potential reassembly. I can't speak to the 4s, but the 7s they build the crate AROUND.
Its just good sense to keep the crates - I recently sold Legacy Whispers and I had kept the crates, which made it very easy to pack and ship them to the new buyer, who greatly appreciated that the Speakers arrived intact with no problems.
So far, that's 5 "for" and none "against". I think you have your answer.......