Hi @Matt - yea, i experience the same, my nodes with the Chinese voltage boosters/converters seems to be dying and my guess has been noice from those components. Im converting more and more over to 5v power from wallsockets and stuff and I also found the 433mhz radios more reliable than the NRF radios still... but I'm really happy, I still have some nodes up that is probably around 10 years now - way longer than I expected I mean, that's sometimes better than bought nodes
Agree with you that learning new stuff is the best with this kind of projects - I have also used the smaller slim nodes and they have some applications. But Im actually moving the other way, to bigger nodes - with modular components. I have to resolder and program everything again so if possible when a node fails I can easily change the component. For example, my gateways now uses "shields" that I can just plug and play on a Uno with easy changeable radio.