In theory, I'm a C.
In practice, I'm a D.
I have often sold two to buy one. Occasionally sold two and bought none.
But I tend to buy whatever appeals to me at the time--not an impluse buy, but I always have something I'm looking for. Currently, that is S&W N-frames.
For example, I've bought two M-25s in .45LC (in addition to one in 45acp) in the last three months, and committed to another yesterday. Do I need four N-frame .45s? No, not really. Will I end up selling at least one? Perhaps/probably.
I just bought my first N-frame .41 mag, 6". If I find a 4" tomorrow, I may buy it as well. And I may sell the 6", because (until/unless Texas passes Open Carry) a 4" is carry-able; a 6" less so. Or I may keep it; both have their place.
To facilitate all this, I have sold a number of pistols and rifles that I do not shoot or carry regularly. This has allowed me to experience a number of different calibers/platforms that I would otherwise be unable to do, and also to rid myself of those that did not meet my expectations (for example, all of my .40 caliber pistols, three .44 SPLs, several Glocks and four Kel-Tecs).