He doesn't care, and he won't change his ways. And that's perfectly okay!

I'm assuming you are someone who closes tabs sometimes. I am too. What you have to accept is that we are the weird ones. A browser is a tool and just opening new tabs for everything is the easiest way to use it. There is very little downside, because there is no need to ever touch an old tab if you can just open a new one. There is no limit on how many you can have open other than what your machine can handle, and even if the browser crashes, nothing is really lost, because you just... open a new tab.

Just accept it. It's hard, seeing a million tabs open really bugs me too, but you're not going to change anyone's mind on the subject.

Some tabs I just want to keep open indefinitely, so I'd like an option for that (maybe automatically, based on a self-defined list of domain names). But with some kind of archiving or reading list and a fully user-configurable deadline, that might work. (I'd put it the time limit at two weeks initially since I really don't mind having a few hundred tabs open, it's only after that that it starts to trouble me a bit and I lose oversight.)