You actually work for Quickbooks and you don't know even know what an Average Days to Pay Report is? How shameful.

We are looking for a report that tells us on average, how long does it take for each of our customers to pay their invoices in full. QBO currently has a field to payment terms that you can adjust per customer, but in their infinite wisdom, they did not provide a means to enforce those terms or even provide access to a report  so you can manually check to see if your customers are paying within their terms.

If I wanted a report that tells me how much each customer owes and when it would be due, which is what your above directions would provide, then I would just check the A/R aging summary.