Usually flying between ORD and SFO I use an instrument to upgrade and I have a pretty good track record. But I saw my SFO-ORD flight for tomorrow was R9 from the time I booked it so I thought maybe a CPU would come through for this one and I would take a chance. I know R doesn't correlate to CPU but there were lots of F seats open. The CPU didn't happen at T-96 and by T-95 it was R4, then R2 at T-72 and R1 yesterday and remains at R1 today. Meanwhile the buyup offer has remained steady and I get constant reminders. Not sure if the CPUs ran out before reaching my fare class (S) or others are taking the buyup or applying instruments or whatever. Whatever it is, it's not working in my favor. I'm going to resist the urge to take up the offer and see what happens after T-24. I predict the result will be a trip to ORD in E+.