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

I tend keep the boxes for gear that would require freight/pallet shipping.

Resist doing it. Major pain in the neck to figure out- and to purchase enormous amounts of packing material- and not having the factory boxes makes shipping them virtually impossible. So, you're then left with only being able to sell them very locally. It's practically worth keeping them in storage somewhere.

In my experience and I’m paying storage fees ($190AUD/month) to save my boxes… because the foam inserts and boxes cannot be easily replaced esp for gear that is over five years old. Manufacturers are not always a reliable source. Values can drop 20% because of this at resale.

And if you are shipping, then nothing replaces original packaging. FedEx total destroyed my ARC D240 amp when asked to pack and ship. They didn’t pack it, they sent it as is then denied the insurance claim on it too.

You can use room space or attic space to store provided you control pests…

But keep your boxes and inserts. If you want to sell and ship safely. I’ve shipped so much gear all over the world UK EU USA AUS Middle East Singapore and original packaging is the only choice that’s secure for components.

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.