The benefits of a smaller collection is more time invested into each one, than spread out over a large group. Prebonsai can be counted...shoot all of them if we want to be real. Because they take our time tending. That's the point on counting...and what we are comfortable with.
Most of the plants I care about (not all are trees) were gifts or are from seed picked up while on vacation or seed ordered because we vacationed out of season. These are my memory garden
it's only 10-12 species. (Un)fortunately, many of my from seed are over-populated because more germinated than I expected. And those that germinated are taking my abuse much better than expected. And there's the problem that to get to a decent 12" tree like I want I need to go through a 12' tree first! Or wait a lot longer.
Another fraction of the plants I care about are "oddities" that caught my imagination for one reason or another. Things like my baobabs and welwitscia...these are all from seed and many have the overpopulation problem!
The rest are to keep me from killing those
Some for the native tree contest...some for the forest contest...the rest just because I was bored and wanted to mess with something to see what it would do...or I tried something because someone said it was hard/not possible, etc...I don't fret none if this group dies