Setting invoice due dates set to the end of an event Merged

Currently, it seems invoice due dates are set to either "x number of days after submitting a reservation" or "x number of days prior to an event." I would love to be able to set an invoice to be paid upon the LAST day of an event. For example, many of our reservations are for gym usage - for an entire season. I don't make them pay until the LAST practice so we don't have to do refunds if they cancel a day. Therefore, I would like to have the invoice due on the LAST practice/date of that reservation. Currently, I have to constantly change the due date to push it back to the end of their season. Thank you.