Over doing it can cause permanent health issues such as thyroid related issues like Grave's Disease. (I've got it now and it sucks.) But if you listen to your body and your mind, you should be ok. Physically, I can go almost 7 days a week as long as I don't push it too hard. 30 miles rt. But pychologically it gets old after 3 or 4 days straight. So I take a break mid-week and either ride in with a buddy or drive. For my weekend rec rides, I make sure to stay as far away from my commute route as possible. I also mix up the commute route to keep it somewhat fresh.