In my experience, confirming previous posters, a few days if nothing unusual happens. In one case I showed up for the previous US flight to my destination, with a BP for my booked flight, just as they were closing the doors. They took my BP for the other flight and let me on with "sit anywhere." Since my booked flight had no record of my boarding, I didn't get credit automatically; had to send in the paperwork. However, it doesn't sound like that sort of thing happened to you.