A normal endurance run for someone aiming for a race pace of 7:00 to 7:03 minutes per mile at the marathon distance would be between 7:30 and 8:30 minutes per mile for most individuals. You are already in that band if you are presently running 10+ mile runs at 8:15 per mile. To put this in context, the current men's world record is 2:11:23 by Lelisa Desisa of Ethiopia at the 2017 Berlin Marathon. The average marathon runner takes about three months to learn their first marathon strategy, which is known as pacing. Pacing involves learning how much effort you can afford to give every step or kilometer you walk or crawl. Your goal with pacing is to avoid injury and reach the end within a reasonable time frame. After you have learned your first marathon strategy, you will need to decide whether to continue practicing it or try something new. If you choose to switch strategies, then you will need to learn how to adjust your pace without getting hurt. This can only be done through experience! Some runners find that switching strategies every few months helps them remain fresh while others stick with one particular approach. There is no right or wrong way to train for a marathon; it's more a question of what works for you and your schedule. The fastest official time ever recorded for a marathon is held by Haile Gebrselassie with his 2:06:58 at the 2008 Beijing Olympics.