7 minutes max is good. Anything longer than that is bad, though you can accept up to every 30 minutes, anything more than that is unacceptable. I used to ride a every 30 minute bus, and I always started checking where the bus was (as opposed to the schedule/time!) long before I wanted to leave. A couple times I made a mistake and arrived at the stop just after the bus left, and was then in for an unacceptably long wait for the next bus.
Mid day you need better service than rush hour. People going to work generally have a schedule and they have input into it - they can plan their day around when the bus goes. People doing errands in the mid day do not know when they will be done, if there happens to be a line when you go to the checkout you miss your bus. When you are at work you have more control over when you leave and so will always make your bus.
When people see your bus system as a way to get to work and a car is for everything else you can do worse service than when you want people to get rid of the car.
Mid day you need better service than rush hour. People going to work generally have a schedule and they have input into it - they can plan their day around when the bus goes. People doing errands in the mid day do not know when they will be done, if there happens to be a line when you go to the checkout you miss your bus. When you are at work you have more control over when you leave and so will always make your bus.
When people see your bus system as a way to get to work and a car is for everything else you can do worse service than when you want people to get rid of the car.