At least for me, the printer is never "done", but it isn't in the "I just need to tweak the blah blah setting every time" sense.

Rather, there's just always something to make better even if the current solution is fine. Say, swapping out the toolhead for a lighter or more modular one, or building another MMU because it can handle softer materials that I print maybe once a year and don't have to use the MMU for, or replacing the hotend with a higher flow or sturider one, or adding more lighting and cameras, or switching the motor mounts to a double shear design to be able to dial accelerations up, etc. Right now I'm working on building a TradRack MMU while planning out a teardown and rebuild of my backup Voron0.2.

I could stop at any point and still have a printer that's near the top end of what's accessible on the market, but the open source 3d printer community moves incredibly fast and it's nice to be able to participate in it.