My first half of the year Dell purchase was made online on June 20; two items posted 6/20, third posted 6/21. Credits also appeared like that, with two credited 6/26 and the third on 6/27.
I’m satisfied so far with the benefits of my new AmEx Platinum card relative to its cost. Assuming my airline credit posts soon (renewed lounge membership June 30th), I’ll have broken even on the fee for the year at that point.