How to identify people likely to unfollow after a follow-back:
Pay attention to their follower-to-following ratio.
If they have significantly more followers than people they follow, it could be a sign they're selective or planning to unfollow shortly after.

That’s why following me is different.
I value genuine connections and don’t play the follow-unfollow game. If I follow you, I stay connected.

That's why I fumigate my following list, to weed of the unserious lot. You unfollow, I return the favour.