I have a flight ORD-MCO that just crossed the 96 hour window. I wasn't expecting a CPU just yet because the flight is showing at R0 (and yes I know it's not a perfect indicator). There are currently 18 unassigned seats in F and it's F9.
What gets me is that I can never discern any rhyme or reason for why a flight sometimes has R inventory and sometimes does not. This flight originally was R9 - I used an RPU to upgrade a companion on a separate PNR, figuring my chances were pretty good to clear with CPU. We'll see!
The last time I had a CPU clear I actually cleared AT check-in, which lends credence to the explanation that the CPU sweep within T-24 actually runs on every checkin.