Good observations and advise. :-) From many ads I seen 'demo' has lasted for years in place - no one suggested otherwise, they just hope you assume its like near new.
The Risks of Buying Demo Gear
Sometimes it’s tempting to consider dealer demo gear to save some cash, or to acquire higher value gear that you wouldn’t otherwise be looking at.
I won’t be doing that again. First, I’ve seen how gear gets handled in stores. Even when bringing in my Nordost Valhalla 2 speaker cables in to audition some Wilson speakers with my amp, I couldn’t believe I had to tell the sales guy not to step on my very expensive cables. I witnessed him stepping on the stores own cables during setup. I felt like telling him to move aside, I will do it.
Second bad experience is I had purchased a demo Innuos PhoenixUSB reclocker to save a few bucks. I now regret not buying new. After a while, I noticed that both the power socket and the USB A sockets were a bit on the loose side, in comparison to my other Innuos products. I sent it back to Innuos to repair, which is at my cost because it’s a demo unit. Thankfully the repair costs are minimal, unlike Innuos products - I was expecting much worse.
In reflection I realize just how many times demo products must have cabling cycled/swapped/changes out, often recklessly. And even before it was a demo at the store, who knows what the history of the unit. The vendor may have used the unit as a demo that travelled around the globe from show to show, for who knows how long. I can’t even imagine the abuse gear used in this capacity must go through.
In my opinion, it’s much less risky to buy used gear from an honest individual seller with a good reputation, as I believe individual owners of HiFI gear take far better care of their gear than dealers do. I think it’s also okay to consider buying used gear from trustworthy dealers when the history of the gear is traceable to one prior owner, and the gear in question has not been used as a demo by the dealer.
Just my take based on my experiences.