A half hour run on Tuesday and Thursday will maintain the endurance gained on the weekend. This is the minimum and results in the lowest injury rate. If you are already running more than this, without aches and pains, you can continue if you wish. As you will see in the 52 week plan outlined in the book Running – A Year Round Plan, more training is needed to achieve most of the time goals.
Learn more about training for runners in Jeff’s book Running – A Year Round Plan. You will find the book at: https://shop.phidippides.com/collections/books-dvds