As a general rule of thumb, if the update has impact on the piece it should be submitted as a new file new fee. An example of an update that would not impact the piece would be reformatting the TMA headlines or grammatical revisions. Another example would be an update to add a new dose format, with no other updates to the TMA and all other information about the original format remains unchanged. If the piece speaks only to the original dosing format, this update to the TMA is unlikely to prompt a new file.
Every case is different as there can be both small (note that even small changes may alter the context of existing claims) and large changes to TMAs, making it hard to define a threshold. All TMA changes would need to be considered in the review of the overall APS.
Remember that significant unsolicited changes during an ongoing review are subject to a new review so if the revision to the TMA impacts the piece in anyway, it is within the Reviewer’s right to send the file back for a new review.