I have gotten the impression the the Rules are adopted by a Rules Committee brought into being by each four year spaced set of delegates. As a new Rules Committee is formed (elected) and set, they can change the rules based upon their political make-up and to favor whoever is in ascendancy with the delegates for that election.
Hence, last time we had all of these Romney centered rules and they exist until just prior to the convention when the new Rules Committee is created and meets.
Thank you for your informative reply!