Say a user purchases a auto-renewing one-month subscription. When can I re-verify the receipt that I'll get a new receipt for the renewed subscription. Do I have to wait exactly 31 days from the time of purchase? Or is 30 days enough?
You can verify whenever you like and as often as you like. If it's after a renewal has happened you'll get the new receipt in the response. Otherwise you'll just get the receipt from the existing period.