Storage boxes. Can I discard high end shipping boxes, and still sell in the future?

I have kept original packaging for all my equipment except, as someone already stated, those things that cost less than $500.  I don’t have room in my house (not even in my “junk room”), but I have a one car garage and I put the boxes out there.  Yes, they take up some room, and I can’t park a car in there because of all the things I want to keep, but I think that is better than getting rid of the boxes.  I have an attic, but I don’t want to risk rodents chewing through the cardboard to make their home.  I think this question involves priorities, unless you truly don’t have anywhere you could store them. 

Flatten the boxes cleanly and if there's custom foam bits just stick 'em in a labeled  bag and store it all at your cousin Shirley's house.

Save your boxes if you can. It is very important for selling and shipping. I have mostly McIntosh and the boxes are critical. 

Flattening a sophisticated dedicated packing is often impossible.  Where it is possible it will certainly reduce the integrity of its structure and invalidate any warranty given by the manufacturer, thus probably negating the benefits of having retained it.

I am fortunate to have ample attic space, but the problem is that boxes for big kit do not fit through the entrance door.  I keep the wooden crates for my Krell KRS200s in the gargen shed.  They have moved with me through three homes.  Where you have no space to store this is indeed a big problem.  Being unable to create space, I cannot assist.

Will never be worth paying several hundreds/mth in storage fees for original boxes