It would help to gradually increase your long run distance each week during your half marathon training. For example, for a 7-week training plan, you can start with a long run of 4-5 miles and gradually increase by 1 mile each week until you reach a distance of 11-12 miles. It's important to note that you do not have to run the entire 13.1 miles during training. Your body can handle the distance on race day with proper rest and tapering.