Author here: I think 4 weekends worth of time is a reasonable estimate, though it was spread out over a longer period — iterating the PCB manufactured in China takes time!
The most time consuming part was the enclosure design.
Hey, thanks for responding! I know it would take me some more weekends than that! :) Have you documented the process somewhere in greater detail perhaps? I'm working on something relatable on my weekends, also involving PCB design and enclosure design/printing (albeit on a more amateurish level of course), so I'm very curious about other people's experiences.
Sorry, but that's all I managed to write — and even that took a while, I kept putting it off. It's always more fun to actually do the projects than write them up later... Also, finding the time to do it properly is more and more difficult.