Just had an odd CPU clearance experience. I booked a ticket late last night in refundable "U" class. I was within the 96 hour window but not at the 72 hour window yet (it was somewhere around T-87 hours). 14 minutes after ticketing the first segment CPU'd and about 4 hours after ticketing the second segment CPU'd. I didn't think UA ran "off" hour CPUs before the 24 hour mark. I'll also note that both flights were PN0 PZ0 at booking, but I know PZ space isn't a good indicator of whether a CPU will occur or not.

-RM