Wash it every week. This includes the insides of the wheels and the wheel wells. Use shampoo every other week. Use a quick detailer throughout the week and after the washes. Use a tire dressing weekly, use a California duster on the insides weekly, vacuum carpets weekly, Use a vinyl dressing once a month on the trim. Touch up the horizontal surfaces of the wax once a month. De-tar the rocker panels once a month or as needed. Clean the glass inside twice a month.
I spend 5-10 minutes on the cars a day and an hour a week. They look perfect pretty much all the time.