I’ve bought numerous trumpets and cornets over the years. I bought specific ones that were cheap enough, mainly because I wondered how they would play. If I didn’t like them, I would sell them for about what I paid, and if they had potential, I’d hang on to them till I decided. Some I kept for years, so eventually I had a “collection”. Realizing that I was accumulating too many instruments a few years ago, I sold a bunch of them that I rarely played, even though they played really well. I designated the others as “keepers”. Those were the horns that I regularly played (some in various keys), had sentimental value, or were really nice antiques. In the last 5 or 6 years, I’ve bought only one trumpet, a deal that was too good to pass up, and still have it.
Presently, I have 3 Bb trumpets, a C trumpet, an Eb/D trumpet, 2 modern Bb cornets, 2 antique cornets, a flugelhorn, and a good field trumpet (bugle). Other than one of the Bb trumpets and the 2 antique cornets, they are all useful to me, so I suppose it’s not really a collection any more.