Our ETA estimates and due times are based on historical data. The problem is there isn't too much data on jobs that big. The more overlap you have the longer it takes to process. The E in ETA is estimated... Sometimes that estimate is a bad one.
Also, on big jobs the outputs files get really big and even though we are throwing over 240GB of RAM at it and 32-64 cores it still takes a while to generate these huge outputs files.
It is still chugging along. Really big projects like this can take 3-5 days depending on various factors.
The progress bar gets updated as it goes through each stage in processing so it will seem a bit chunky.