Going back to four days per week of running

Two weeks ago I added a fifth day of running and have it up to two miles. However, I've been reading http://www.jeffgalloway.org about getting sufficient rest. Jeff suggests that runners over 55 only run every other day. I've done well on four days/week, and I think I will abort the fifth day and only run four days per week. That gives me a 33 mile/week schedule, which is sufficient for half-marathon training, especially at my age.