Think about your regular old land line phone services. Another very important issue is WHEN and for how long you will use your wireless phone. While you probably want to have it on hand ready to use anytime, there is likely a certain part of the day or certain days of the week when most of your calls will occur. When you use the wireless phone, goes hand in hand with where. If you have determined that you will make most of your calls during your commute, that in turn also narrows down the time of day that you will make most of your calls.
Most people make their calls during regular working hours on regular work days.
That's why most carriers define these hours as peak time. Sure - you want to use your phone everywhere, have every feature available and use the phone constantly. You can do that - but you'll have to pay for it. This isn't your plain old telephone service. Even if you get a great deal, wireless is more expensive than regular phone service.