no advice on the preemie thing, but a few thoughts on being an "addict" to a daily workout. I say that tongue-in-cheek, but just partly. (I'm one too, biking every day keeps me sane and stable).
A large component of my habit, I think, is the comfort of routine, a steady dose of endorphins and stress relief. It's a healthy addiction, but an addiction nonetheless. Consider that once this habit is getting in the way of something else you want to or should do, you may be seeing the downside of an addiction. Physically you can keep in adequate shape (unless you compete) by walking and swimming for a few months.
If I were you I'd definitely get a second opinion, but also give a thought to why exactly biking and running is that important to you. Not least it could be useful if you ever get injured and have to do some alternate training for a while. I had to, last winter and it was an eye-opener.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett