Iowa will recruit to the end if they are the guys they want. Think Alaric Jackson, Noah Fant, Trey Creamer, Smith-Marsette in the last couple years.
If Iowa thinks they have a legit shot, they keep after them. They don't typically let recruits just jerk them around tho. If you tell them you are gonna sign in Dec I could see them moving on if you were just holding out for a better offer. As always it will be a case by case thing. Iowa will continue after some and cut ties with others.
What? Jackson, Creamer and Marsette all committied to Iowa literally hours before Signing Day. This has nothing to do with my point.