I interpreted your question as, "how much gear do you have that you are not using?"
I have tried to simplify my system(s) over the years by using SS gear that remains powered up all the time (got rid of the tubes) and by weaning myself off of physical media. Currently, I have a couple of duplicates but those are mostly active situations where I recently made a change or where I am in the process of comparing options. Thankfully, I do not have a pile of boxes of gear that I don’t use. I do have some older gear that I haven’t been overly motivated to part with, such as my first NAD system. Somebody interested in vintage systems would probably appreciate that stuff.
Where I find excess is in cables and small boxes. Since I have constructed many cables over the years, I have a couple of plastic tubs full of pretty good cables that I could (and should) probably sell. I also have a number of small boxes (mostly digital enhancement stuff), which is why I remain mostly skeptical about the benefits resulting from small, magic boxes that cost a lot of money.