At one point, I had more than I shot or carried. So I thinned the herd a bit. These days, if I don't carry it or shoot it somewhat regularly, it is gone. That got the overall population down to a manageable level.
Then I started a practice. Once every six months or so, I make a list of my handguns, starting with "if I could only keep one" and then listing them from most desirable (which usually means the one i carry most) to the one(s) that are harder to justify keeping.
I keep and review those lists to see how my perceptions change over time.
And when I get to wanting something new (or used) I look at the bottom of my latest list, and determine if I want the "new" one badly enough to sell the one (or two, or whatever) at the bottom of the list.
It has proven to be a very workable system (for me).