Factoring companies are limited in the type of financing they can offer by the 90 day buy-back period. In other words accounts receivable financing is only for businesses that issue 30 day net term invoices and have a history of getting paid on time. If the cash flow model of your business is not getting payment for work completed within a relatively short time (vs. quarterly or annually) then factoring might not be a solution for you.
The reason stems from the arrangement a factor has with its funding source, usually a bank. The bank lends money to the factor who then turns around and makes advances to their clients. When calculating the available credit to the factor, any outstanding invoice over 90 days is considered a non-performing asset and is deducted from the available credit line.
In some cases an errant invoice does go over 90 days. In these situations a recently finished job with a new invoice is swapped for the overdue invoice. But as a business model for all advances, with factoring it does not work.
Regarding the flow of money and credit, all the pieces of the puzzle interact with each other and rely on payment terms being met on time.