When to update audit fields? DDD

Question

I have a Meeting Object:

Meeting{id, name, time, CreatedBy, UpdatedBy}

and a

MeetingAssignee{id, MeetingID, EmployeeId, CreatedBy

Answer 1

You could possibly make the call to the audit service from the service layer when persisting or updating the entities, with the audit service having being injected into any services that require audit functionality, and persist the newly created entities as quickly as possible.

I see how it could be hard to work out how-and-when to audit, especially if your entities are going to exist as usable entities in the system sometime before being persisted. Even if they exist for some time before being persisted, maybe you could create in-memory audit data, containing the details of their creation and then persist that when the entities are eventually persisted. Or have the created-by, created-on, modified-by, modified-on, etc. data set as private fields in the entity and write it out to an audit log when the entity is persisted?

I'd be interested in what the trade-offs would be.