Well, we have 26 commercial breaks every day, and each commercial repeats at leas three times per day. There is a solution for this. All the commercials should be imported as "Commercials", not "Music" or anything else.
Second of all, you need to make m3u's (via Playlist Builder in RDJ) that contains the spots for every commercial break. After that, go to events, and create for each hour an event that loads m3u coresponding to it. Believe me that all the files will play without any issues, even if you have a restriction of some hours per song.
I have three stations in administration and I never ran into problems when it's coming down to commercials.