I’ve noticed a lot of 3d printer owners spend a lot of time making replacement parts. Is this is hardware equivalent of a programming language that compiles itself? 
More like a self-replicating robot… or a self-replicating printer… You know, a Rep-Rap.
It’s good to have backups in case something breaks, and initially it’s good practice making real stuff besides calibration cubes.
Plus you get to customize your printer. Just because it came with black or white parts, there is nothing that says they need to be that color.
More like owning a vintage car… That can make some of its own parts. There is always something needing fixing replacing or upgrading!
Print em if u gotem
Of course u can always keep a backup printer
It could be the equivalent of finally getting source code and a compiler for your OS. The temptation to adjust features and fix issues in your favorite SW sounds equivalent.