"Never sell a gun." Used to feel that way.... I see no problem selling a gun you have no use for. When I started buying guns, every single one had a specific purpose. When the purpose ended, I eventually sold them. These were mostly long guns versus handguns. The handguns are harder to part with for me.
As time went on, I pretty much covered all the bases and things that I first started buying became somewhat collectible (Colts mostly). So, I stopped shooting them although I would shoot them if I felt like it or need to. Not really going to hurt a gun that I have shot a bit in terms of its collectiblity (value). Shot is shot. I moved into the collector ranks over time buying really pristine guns with no intention of ever shooting them. I separate these out of my consideration as they are purely to eventually sell down the road if I can bring myself to part with them. It is hard even when you loose interest....
As I get older, I am less attached to the collector stuff and likely will begin to divest myself of some of them and raise a bit of money for other purposes. I am not in the market for any gun at the moment although I would pick up a "bargain" if one walked in the door. I went from buying a couple guns a month to one about every couple of months, to a couple a year at most now.
In the past, there have been gun shows where I left with as many as 5 or 6 new guns. Those days are past and I have no interest to rekindle that kind of thing. So, sell stuff you have no use for if you want to. Or keep it as part of a "wealth acquisition" effort. Good guns really don't go down in value after owning a couple years overall. I think of them sort of like I would a gold coin.... valuable, but not so easy to sell.