HN user
This shipping hack may apply, or it may not.
Search for a local warehouse that provides order fulfillment services and see if you can have them ship your benches.
A place like that ships enough packages they can usually get lower shipping rates than other businesses. I own a company like that in Ohio. With my rates it costs perhaps $30 to ship a gaming PC to California... for an individual it might cost $75.
Increase your prices.
You may be afraid to lose business, and that could be the case if the partner company is your only source of clients.
I did freelance consulting for a long time, and each time I found myself overwhelmed like you I increased my prices. I did lose some clients, but overall I made more money for doing less work.
Here's what is _supposed_ to happen with perishable goods: https://sellercentral.amazon.com/gp/help/external/G201003420...
tldr; Anything perishable is supposed to have several expiration date labels on it in large format, and nothing can be sent into Amazon that expires within 90 days. Amazon says they will dispose of anything received with less than 90 days remaining before it expires.
There are a number of things that could be going wrong here. I operate a supply chain company which works with 3rd party sellers, so I'll focus on what I'm exposed to.
One issue could be Amazon's labeling requirements. They actually require a separate label in MM-DD-YYYY format to be affixed to each product. This sounds good on paper, but in reality it means the seller or sometimes a 3rd party warehouse can put whatever they want on the label. Generally, sellers are honest about this, but mistakes do happen and Amazon doesn't necessarily verify what these labels say.
Beyond that, commingling can compound the issue. Say you have 5 businesses selling the same product, and one of them is fudging their expiration dates. It becomes fairly difficult to track down which seller is fudging the dates. This is one reason I recommend all my customers not commingle their inventory (it's an option the seller can choose).
Supply chains can also have wildly varying temperatures. Many sellers choose to work with climate controlled warehouses, but don't consider the trucks used to move their inventory aren't climate controlled. It's highly possible a product meant to be stored at 70F will sit in a 110F truck for 3 days before being checked in at Amazon.
Sellers have the option about whether their inventory can be commingled. Also, when there is high fraud potential or a large number of complaints Amazon doesn't allow commingling stock.
I operate a supply chain company who works for Amazon 3rd party sellers.