I'm running my first marathon at the end of April. I'm not planning on running a marathon again until spring of 2015, but I do plan on doing some 10 mile races, maybe a couple half marathons, etc., in between. My question, however, is how long should my long runs be to maintain my fitness? I want to see how I do in my first marathon, and though I don't do speed work now, I plan to start after my marathon. I'm only 19 years old, so I want to continue improving on my times. Should my long runs continue to be 15-18 miles? Should I focus on upping my daily mileage instead? Right now I do 6-7 miles every day except my long run day. But I'm not sure what I should be doing when I'm not necessarily in the training phase for a marathon.