I would definatly recommend to take days off during the week. Your body needs time to rest. If you over do it you will increase your chances of injury. I know this because I used to run 7 days a week and I ended up getting a stress fracture. The American College of Sports Medicine recommends that people participate in cardiorespiratory training 3-5 days/week for around 20-60 minutes. So I would say to up the intensity of your workouts and also add some variation. I do a lot of cross training. I start off on the elliptical, followed by running and then I finish with some biking. Cross training is more challenging for your body, plus works more muscle groups.