iPhone application Verify Recipt on server during apple testing

quick question because I can't seem to find info on this but I h开发者_如何学运维ave an application which is a paid recurring subscription app that is submitted to apple. As it stands now we verify store receipts using Apple's sandbox url on the server. While apple is testing the app (before it is approved) should we change that url to production or wait until after approval? Does it matter? Thanks!