I can only speak for myself, but when I say two day battery life would be good, it's not because I want an actual two days, but because I want to know that it will last me a full day without having to babysit or worry about it.
I don't think you're wrong about getting into a routine. That's effectively what one would have to do with any such Watch. And I think once you get into much longer battery life you run the risk of just forgetting to charge the thing at all and then one day it's dead (has happened more than once with my Fitbit lol; I too try and charge while showering and that seems to be enough to never require an overnight charge).
I mentioned above my wife's battery woes. I have no idea if they're typical, but I also know she isn't doing anything beyond responding to messages. I think a solid 12 hour day without your watching going dead is a reasonable ask, if not from the technology, then from the product. What I mean by that is, if in asking too much from today's tech, this just means what exists currently doesn't yet meet my needs. I feel like $$500+ is a lot of cash to be at the mercy of a plug with yet another device.