It's pretty accurate. I had some heat elements for the brooder in the mail that I needed a few days ago. At 2 O'clock this morning the last update was when they left Compton CA at 3:30 am on the 9th. Checked back at 4 am and the package had arrived at my PO. It is now out for delivery.
They usually use another company so while the package is in the hands of that company there is no update. As soon as the USPS gets their hands on it, it goes into the system.
I'm sure my package didn't go directly from Compton CA to the Florissant MO post office so the 3rd party shipper didn't or doesn't have the ability to update progress on the way.
If it isn't reporting that they're at your PO or out for delivery by now, you're probably right and you won't see them till Monday.
At least they're sitting somewhere and not bouncing around. Have faith.