This isn’t an Apple thing, it’s a “laws of physics” thing. The parent is suggesting that you do your intensive computing on a computer that isn’t battery powered so as to prolong your laptop’s battery between charges. “Apple life” in this case is having two days between charges rather than a few hours.

When did that happen?

Asking as an iPad owner.

It doesn’t matter whether it happened or not. The comment says something some people want to hear.