I used to track these changes in conference schedules for the SIAC, Big 8 & PAC but haven't in the last several years as it takes up a lot of time.
In 1992, the SIAC switched to having the rivalry games in the last week of the regular season. The schedules pretty much stayed the same and they used to rotate weeks 3-6 (week 3 would become week 4, 4->5, 5->6, 6->3) for a while. With the addition of Jasper & Vincennes, they pretty much had to blow the schedule up, but did keep the rivalry weeks intact.
Back in the day, the city schools would rotate who played on Thanksgiving. (Here's an article from 2007 I wrote that lists the Turkey Day games and you can see how they rotated).
Putting schedules together is not an easy task, especially with balancing home games, teams dropping out and joining, rivalry games, etc.
Definitely following this conversation. It's always been interesting to me and glad to know there are others too 🙂