Wow, I am really fortunate in the way IHG IT has handled my Accelerate promo. All of my tasks, other than the one requiring use of a Chase IHG Select for a booking, have posted within several days, and I certainly expected that posting on the Select task would not occur until after the billing cycle had ended. My most recent stay, which helped me complete the task requiring two stays of four nights or more, ended at 9 a.m. Sunday with checkout. By 3 p.m. Tuesday, the points from the stay had posted as well as the points from the completion of the extended stay task.
There is no consistency that I can see with how IHG IT has handled promos across different members. Some have had problems, some have not.