I had the same issue as the many others that my $75 purchases were showing up as being on 1/1 so i spent a whole bunch of time chatting with them and they manually gave me all the credits.
Anyway the coolest thing just happened, almost all of my accounts just received the credits (3/1) AGAIN!!!
I guess the 90 day thing wasn't bunk as i had thought, but all the accounts that the manual credits are listed as "credit for billing inquiry" were recredited, but one of my accounts when manually credited was listed as "amazon offer" did not get recredited.
Anyone else get lucky enough to pull $50 off $75 at amazon like me?