Whenever you like, honestly. It’s mostly a nice acknowledgment to the poster that you appreciated their post. Unlike commercial social media it’s not sending out anything to your followers that you interacted with it (at least last I checked).

I think many people boost more than favorite because it functions a little similarly in regards to acknowledgment, with the bonus that it helps share the post to others which is even more relevant in federated networks than on centralized platforms.

That’s the corporate web: sterile, intrusive, manipulative, endless list of negative descriptors.

It’s why you gotta take whatever’s of value from it and put it elsewhere so you can get away from it as much as possible. Then spend more of your time using the public web intentionally for things that you enjoy and interest you, instead of allowing the corporate web to use you.