A second realization came a few years ago when I looked at what was still available of my Magic: the Gathering original art, being the most notable of the artwork I've created. In all my years working on the game, I only had one piece that was held back as not for sale, to keep, and that because my wife also got her claws on it. That would be Counsel of the Soratami. And that was just because two collectors on the verge of purchasing it early on didn't do it. For which I thank them, now. Within that body of work, there are maybe 3 other paintings that I wish I had not sold: Dance of the Dead, Soul Warden, and Balance. But it's hard for an artist who makes his living exclusively through the sale of art, to not sell art. When the market for Magic art began to change to where I could no longer gauge the worth of the historical pieces, I pulled the rest that I still had for sale and "vaulted" them, including all preliminary drawings.
The last thing that affected me was visiting for the first time the home of an older artist I admire, whose career has been much longer than mine and more successful than mine. I was dumbfounded to see the selection of originals still in that artist's possession--pieces that were popular from when they were created, that surely would have sold instantly then or any time since, and some of which were almost as old as I. Yet somehow, this artist had been prescient enough to know that they were important works, and never sold them. Having had a more successful career, it may have been easier to hold those pieces off the market for income's sake. I don't know, but I suddenly felt very foolish about some of the pieces I let fly too easily. This artist's history was there, and they had a great collection of works to either pass down as inheritance or to parcel off through retirement. That sealed the deal and turned my concept of a "vault" into something more concrete.
I like systems, so I kinda formulated one for myself, and here's a little of how I think about things:
For new art, I might choose to vault something immediately, but mostly I'll make things available. From the time they go on the market, I might give them a year, maybe a bit longer or less, before I decide to pull them from being available and vault them instead. For Magic art, I'm defaulting to a shorter time frame, for other works, a bit longer. But the idea is the same: make them available for sale for a bit, then put them away.
Once in, they're likely to stay in for quite a long time. I'm thinking at least a decade. As I approach 25 years as a professional, some of that art has been vaulted almost that entire time. But the idea is after some many years, to reconsider a few pieces and make them available for a limited time again, and then put them away again if they do not find a home.