Excerpt from Racing Multiple Marathons: Everything You Need to Know by Jenny Hadfield:
Once upon a time, runners would race long distance events for one purpose: the fastest finish time possible. They would focus on one core race per season and put all their efforts into making it their best performance.
Today, runners are going for frequency of events and finishing multiple races in one season or throughout the year.
Both are excellent challenges, but you can't use the traditional training formula for a new-age race goal. (You can, but you're likely to end up hurt, frustrated, and completely unsatisfied).
The key to successfully racing multiple long-distance events in a short period of time is to change your paradigm and look at it from a different angle.
Read the full article for more details.