I don't think there really is a deadline. If a prospect wants to transfer/enroll somewhere and they have the time (even a few days) to get them through any paperwork they can enroll. I'm sure recruits have decided a week before school starts in August in some cases.
Assuming they signed their NLI's already, my understanding is that the releases will have to be granted by the school, but typically always are when there is a coaching change. So the "deadline" will be whatever amount of time the school permits them to meet the new coach and make a decision. Would imagine it would be sooner than later though.
If they are just verbal commits, then there is less of a definitive deadline and URI is in more limbo unless they decide to pull the offers and go in different directions (if they believe the players are not going to sign).