When the email responses have bounced around five times.
When the chats are upward of ten responses and each reply is getting lengthier.
When side conversations are starting to splinter off.
You might have a different set of thresholds in your mind, but having the threshold is important so you can go “I think we need to get together and talk this out.”
Your first response from someone might be – “Oh we don’t need a meeting, we’re almost there” – great, let’s have a call and get their faster, because unless everyone is saying they are almost there, and the conversation goes on for another twenty replies, you should have called the meeting.