> I am still trying to discern a pattern in all this.

I don't work for Amtrak, so this is simply my conjecture. There are two transactions that can delay posting of points. I assume that the conductor has to download the data in his scanning device at some point (which may not happen immediately after a trip). Then that travel data has to be batched and uploaded to the Guest Rewards database. If the conductor's download just misses one of the batch updates, then you get hit with a double delay. I've had points post within 2 days and I've had some literally take the entire 3-4 weeks that Amtrak says to allow. Clearly it's not a completely automatic process or they'd all take the same number of days to post.