If touchdown is 12 midnight, doors should open 12:10 am, immigration by 12:20-30 tops (if you're up front), bags should be waiting for you, q for taxi (5 minutes) and you should arrive in hotel in town by 1 am latest. Done it a million times - note surcharge on taxi after midnight.

You can ask for late check out or at worst, leave bags with concierge and enjoy the city. If 7 pm departure, if you leave for airport by 5 pm, you'll still have time to explore a few shops in the terminal.