During the PADI IDC Knowledge Development Presentations we teach PADI IDC candidates to tell their student divers the value of learning the information. This is in the form of "how and when" they will use the information themselves. I always suggest that their example is ASAP, because this creates a need to learn. If the example is sometime in the distant future then the divers tune out rather than tune in.
The same is true of the information you learnt during your PADI IDC. If the information had a direct impact on your imminent PADI Instructors Exam you stored it in your brain and chances are, you can still recall that information even now. However, there was a wealth of information and great ideas that were discussed that was not directly connected with the PADI IE which you probably thought would come in very useful once you had started to teach, but can you remember it now?
Sure, you get to revisit the subjects when you enrol onto a PADI IDC as a PADI IDC Staff Instructor, but you have to wait until you have earned PADI MSDT before you can do that. Now that the PADI IE is out of the way and you have freed up some brain cells, revisit the subjects, it will be a revelation to you.