My episodes (5 altogether) have been spaced months(usually years) apart, with the last one being 6/17/07. My EP says he'll move towards a "pill in pocket" approach if/when I get out again. In the meantime,I take a good amount of fish oil and a baby aspirin to stay nice and thin just in case something does happen. With the frequency of your bouts, I would imagine you would be on some type of blood thinning protocol.
Diltiazem is the same as cardizem I believe, and I have had that in the ER. It does help to control rate (somewhat) during episodes, but since it's a beta blocker, it might not be the best option during the times when you are in NSR for those 2 weeks. You probably don't need your HR reduced any further since , as a runner ,it's probably already on the lower end. My primary guy was itching to do this, but my EP (who is a runner thank God) saw that appoach made no sense.
Talk with you doctor, or better yet seek out an EP. I would imagine that thinning your blood and taking a rhythm control drug (rhythmol,tambacor, or others) may be the best option for you. Of course, with the frequency you suffer with, an ablation procedure may be a good option. Your EP would essentially induce afib and then "map" your heart's electrical pathways. After targeting the "haywire" areas, they would zap them with a laser or freeze them to stop these electrical pathways from interupting the normal rhythm. The catheter is entered into the groin or neck, and you are heavily sedated but awake. Sucess rates are pretty good, but often people need one or two more procedures down the road. Still, with the frequency you suffer with, this may be a solid option. Good luck