It usually takes between 2 days and a week for mine to switch from "Completed" to "Received". Once it goes to "Received", you're in the clear, you won't hear anything else unless there's an unexpected problem. If they have a question while reviewing your report, you'll get the question before it switches to "Received" status.
Completed - you have submitted it, it's waiting to be reviewed
Received - They have reviewed it. In my experience this means it's ready to be paid per their payment policy.
Shopper in California's Bay Area