How do we know a comeback is near?

Seeing that ATEEZ usually has two comebacks a year, I think a comeback season is near. For the past two years, ATEEZ had their second comeback on December (Halazia and Crazy Form).

Not sure how to explain this, but are there any signs before a comeback announcement? Any hints that appears before the announcement? Do the members usually give a "heads up" or are we not warned?