Is it a worse misallocation, I wonder, than doing what most people do with Raspberry Pis, which is leave it in a drawer ;-)
The 3B was my Octoprint server for the longest time while I was testing the 4B for a product, but for reasons I don't really understand, the 3B isn't quite punchy enough for Klipper, when it fully should be; it drops connections to the printer. I think any of them may continue to have some uses but perhaps not till I move to a new place.
Haven't gone for a 5B or Zero 2W yet, don't really need to. Rather more interested in what happens with the Picos these days.
I think I have one live one running in my house, but I haven’t checked on it in a while and it might actually be dead now.