I've noticed the anaerobic thing in my worm bins for sure, because that's the only time they ever stink. Wet paper seems to make a pretty effective barrier. So I periodically (i.e., whenever I think of it and feel like it) stir / fluff /
root around the bottom, poking through and tearing paper, to get oxygen down there. That's also a good time to deal with excess moisture or an excess of rich material by adding carbon-rich stuff. I haven't noticed a need to do more than that, though it seems like if you could flip the whole mass easily, that couldn't hurt.