It's one of the metrics, but having kids and thus less time for hobby projects, the more profitable a side project, the more time I can dedicate to it (and reduce my freelance work). And thus I can use it more long-term.

With non-breaking tech, I can focus more on features and monetization instead of updates and debugging.

I still give some space for experimentation (re: frontend I'm interested in learning more about Mithril.js and Svelte), but I don't go all in and risk long-term profitability.