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

Also, it's like buying a car. You are not putting the thing through an X-ray before you to assess if it was properly taken care of, so you assess the condition based on a lot of little things. Preserving the box is one of those and as said before, it boosts the price. 

My experience with buying and selling is that items that have original packaging make the market broader and in general garner a higher price and sell quicker. Many buyers won't consider buying without it. It is not because material is not available to pack items correctly. It is that you have to trust someone across the country that you don't know to properly pack an item for shipping without the original packaging. There are far too many that can't or won't properly package an item for shipment. It is not cheap to package delicate electronic equipment properly for shipment.

I am lucky in that I have a large, dry storage building and keep all packaging no matter how long I intend to keep an item. When possible, it is best to have it on hand.. 

Don't get rid of the factory boxes.....there are a lot of people that will refuse to consider buying used equipment without the factory box....unless it is sold at a big discount.  If you need service work some companies require you to send your unit back in the factory box or if you don't have one will sell one to you for hundreds of dollars.  

Currently saving original boxes and packing but wondering how much abuse can cardboard boxes take before they no longer protect the contents? I double box esp if the original box has seen better days.

Also can anyone comment on replacing or supplementing packing material with expandable foam?

It is crucial to think about the potential effects on selling your products in the future, even if it is understandable that keeping all of your equipment in shipping containers might become cumbersome and expensive to store. Given that they project an air of quality and professionalism, expensive shipping boxes can increase value and appeal to potential customers. If storage costs are a problem, though, you might look into other possibilities. One option is to downsize or repurpose the boxes, disassemble them, and store them in a more compact way. Additionally, you might think about purchasing shipping containers, which offer an economical and effective way to store items—including your equipment boxes—while lowering costs.