Chicago USCIS PO BOX: How often do they pick up their mail?

[R78]

Box sizes are standardized at post offices. Assuming USCIS bought the biggest box, it is enough to hold 50 packages+overflow.
I would not be surprised if they collect mail every 1-2 days.
The issue might be that they may not have enough personnel to open the packages, quick review of documents & cash checks right away. So a package that is picked up the same day may be reviewed 5 days later (with the receipt date still being the postmark date)

[Xokoow]

I was waiting from 4/4/2021 and today its 4/22/2021 and still say ready for pick up somebody can help??