And here is the output, being drawn off by the ubiquitous hanging weight (out of sight). The spools take just under two minutes to empty, ready for unravelling, rewinding, and then the knitting process is repeated. No extra yarn required!

Bigger spools can certainly be used (I started out with Faceplate spools, and pretty quickly decided that they were not for me), but then you have to think about how you are going to handle it all. Logistics do matter!