there is no policy for when a no-show kicks in. it is handled on a case by case basis and differs from hotel to hotel (I know that is not what you wanted to hear).
Usually when an a Night Auditor performs his audit (a program that takes about an hour when the whole reservation system shuts down usually between 2am and 5am), he will cancel any remaining reserations and charge them with a no-show fee. If you do not show up on the night of your reservation (even if you have a 10 night reservation), your entire reservation will be canceled and you will be charged for your first night's room and tax. Assuming you have not communicated at all with the front desk, when you arrive the next morning at 7 am you will have no reservation and your room may have been sold to someone else. Your previous reservation and rates are not honored.

a rule of thumb, always connect with the front desk and let them know if your plans might change and they will always try to work with you, and save a room for you.