Except for the SPSSI dark days in 2012 when anything was possible and calls to the MPSC were plenty, new UA and old CO have been very consistent for me in 11 years of flying them -- 3pm-3:30pm Eastern time, 2 calendar days after departure of the [first|last (I'm still not 100% clear)] segment in that trip sequence.

It seems to be very batch oriented processing and also seems to (roughly) coincide with the flown segments falling off of the PNR -- what I've assumed happens is that a process gets fired to remove "expired" segments [ETC status = flown/used] from active PNRs, those segments are fed into the MP engine which then calculates credit (RDM/PQM/PQD, bonuses, eligibility) and then posts to the account.

I'd love real-time posting -- or at least posting before that survey email (which usually arrives in my inbox shortly after I've forgotten anything specific about that flight sequence), since I do log/reconcile everything with my "Forecasted" accruals... but I don't think 48ish hours is terrible, especially since its consistent.