I was just about to step out to photograph some for sale (still am ) I have to agree with Gaines, although I have nowhere near his collection or quality. Nonetheless, i did collect and was fascinated by classic and antique springers, just the quality stuff. When the bug bit me, I had to try them all (*well, lots...) and eventually found that while I did admire and cherish them all, only a few got shot regularily enough to justify keeping them.
What really became my hallmark moment of realizing I had too many was when I added up the cost (I kept records of all sales) I realized that although I had always lusted over a fine english double rifle in a classic African calibre, I could never afford one. However, in just 5 years of collecting, I had spent over the cost of one on airguns alone. Bit by bit, it adds up.
A couple of years ago I too adopted the "one in, one out" technique of collecting, in order to keep things realistic. I use this principal in all areas of my life, as I am nearing retirement and dont want a huge pile of things to weigh me down, so to speak.
I am now happy with 2 TX's mk1 and mk3, a Webley mk3 and a Waklther LG55 Tyrolean. I do not forsee ever buying another, and will be listing a bunch later this week.
I am forever gratefull that I got to experience so many wonderfull rifles, the joy of ownership, and in many cases, the fun of restoring them. I am nowhere near done with Air Rifles, (I shoot em every day) but I have found what i like, and what suites me. And usually made my money back, so the hobby has actually cost very little. Hard to beat a hobby like that , eh ?