Terminal float is where planned Completion is in advance of the Completion Date. If the Contractor has used this up due to their own risk items then that is their gift. If you have an Accepted Programme where terminal float has been used up and planned Completion/Completion Date are the same, there is nothing to stop the Contractor to have a better month next period and if their planned completion is now earlier again by say a week, then you ave no choice but to accept their programme (assuming it ticks all the other boxes) and they do indeed have terminal float again. This could be increasing or deceasing each period throughout the project.
This period is Contractor owned, and can not be absorbed by compensation events i.e. if there is a delay to planned Completion by one week due to a CE, then Completion Date should move by same amount.