I never said that's not possible, I said you can't design your systems to assume that it's one of those things. It is certainly possible that after 10-20 years a system might never have needed an update, but you didn't know that when it was built, purchased, or implemented and assuming that will be the case is undeniably irresponsible.

> And before you say "even if the code is fine it's old crypto, it's insecure", when was the last time someone got pwned because they ran 25-year-old TLS 1.0?

The correct answer there would be "none yet", and there's no guarantee it would ever happen, but there are known weaknesses so it's always a possibility. Again, not saying everything will need to be updated regularly, but it's not a good call to assume your thing will never need it.

Let's look at this from another angle. Presumably if you have a desire to expose a device to the internet as a whole it's because you either want it to be able to access external resources or you want external systems to be able to reach it, and the outside world has this tendency to move on over time if protocols are flawed, even if those flaws don't matter to your device. If there's a process for updating regularly, this is no big deal. If there isn't, your thing is going to get progressively more annoying to use wherever it needs to interact with systems outside of its control.