How long after a DM should a lead still count as coming from that post?

As long as the DM thread stays one unbroken conversation, however many days that takes to close. Only start a new clock if the thread goes fully silent for about 90 days and the person doesn't reference the earlier conversation when they come back.

Ad platforms cap attribution at 7 or 30 days because a click is a single event with a clear expiry. A DM is different: it's an open conversation that can run for weeks without losing its connection to the post or story that started it. Someone who replies to a story in week one and books in week ten made one slow decision, not two separate leads.

That's why a fixed day count is the wrong tool here. Instead, treat the thread itself as the unit of attribution. For as long as the conversation stays continuous, credit it to the post that opened it, whether that takes 3 days or 70.

The one case that needs a cutoff is silence. If a thread goes fully quiet for around 90 days and the person then messages again with no reference to the earlier conversation, treat that as a new lead credited to whatever started the new thread. If they do reference it ("following up on that quote"), keep the original credit even though months passed. Ninety days roughly matches the slow end of a typical sales cycle and the longest extended attribution window Google Ads allows for a single click, so it's generous enough to keep real, slow-closing deals in the count without stretching credit past the point a client would find believable.

The full method is in How Long Should an Instagram DM Lead Stay Credited to the Post That Started It?.