Covering 26.2 miles can take runners anywhere from just under three hours to over five hours. It takes time to prepare the body to cover such a long distance and to be moving for that length of time. As such, runners need to allow adequate time to build up to the effort. It is unadvisable for new runners to jump into a marathon training plan as the incidence for injury is very high. I recommend starting with a shorter race and taking six months to a year to build to the marathon distance. Following the 10% rule will ensure that runners do not build too quickly. They will remain healthy and find faster fitness gains by moving slowly through their progression. Only increase total run volume or individual run distances by 10% each week. If a runner can comfortably cover 20 miles on a training run and maintain a weekly training volume of 30 to 40 miles per week for at least three weeks, they are likely ready to jump into the marathon distance. While some runners are concerned that they never cover the entire 26.2 miles in training, that is okay, they are still ready for the race distance. The rationale for not running 26.2 miles is that the recovery necessary to accommodate for that level of overload impedes on subsequent workouts. In other words, it takes too long to recover from a 26 mile training run for it to be beneficial in training. Instead, focus on quality over quantity. Covering 20 miles on a training run takes less time for recovery and enables quality workouts to follow in quicker succession than if the effort was a full six miles longer.