Why not at least 9? Or 5?

I think it would be best to focus on the deterrent effect for the future: we need a law that makes this business strategy not viable. Not on punishing bad behavior that already happened. Maybe such law already exists, but we need more enforcement. Or a better thought out law.

I don't think it's important if _that_ person gets jail time. I would not particularly rejoice at the news. But if somehow this practice was made impossible or impractical, I'd

One of the reasons for punishment is deterrence. It it becomes clear people consistently go to prison for doing something like this that will reduce the likelihood of people doing this in the future

Or at least make it mandatory to disclose such behaviours before purchase. Failure to disclose should result in the vendor and the manufacturer becoming liable for the repair/replacement costs (with the vendor similarly able to push the costs to the manufacturer if it was not disclosed to them either), as well as any actual damages resulting from the failure of the product.

Need the jail time and a safe harbor if the behavior is fully disclosed in advance with all advertising (a simple phrase will do such as: "Useful life limited to ~10 years, details at xyz")

Some people might be fine with a product with a known lifespan, or want to pay more for the unlimited life version

The penalty should be more like corporate death than individual prison, as that often gets fobbed off on some scapegoat rather than on the actual manager responsible

As much as I agree with the sentiment and desired outcome (better/longer lasting products), detecting and enforcing that seems horrendously difficult. A great example is the VW (and others) emissions scandal. They evaded detection for years despite bringing the product for inspection. In the case of this thermostat, you would have to prove it wasn’t a bug and instead malicious intent to send someone to jail. You’d need records of who said it needs to be this way.

We can’t send arbitrary people to jail for bad designs. I don’t think many people would be an engineer if you knew there was possible jail time if you shipped something with a bug.

You can fix some of this by having competent and independent inspection, which this seems to be. The rest - perhaps you can't litigate, but you can publicise, with details, and perhaps something a consumer rights watchdog or public body would pick up.

You can already go to jail for engineering something with a bug, if it has bad enough effects and the prosecution can prove that a reasonable engineer should have fixed the bug or not written it.