I'm not sure what math you're using. 12.9 MET for running * 3 hours * 60 minutes/hour is 2322 MET-minutes, so just 3 hours of running is sufficient to exceed the 2200 threshold. 36 hours of running would be 27864 MET-minutes, of course it is too much. But 3 hours of running in a week is quite easy to exceed, e.g. if you run half an hour every morning.
There are some studies which suggest that the artery buildup from frequent running is not bad, but these don't take cancer or other factors into account - in contrast all-cause mortality is one of the most comprehensive statistics available. The drawback is that although it gives you a number, that number might be affected by unknown variables.
There are some studies which suggest that the artery buildup from frequent running is not bad, but these don't take cancer or other factors into account - in contrast all-cause mortality is one of the most comprehensive statistics available. The drawback is that although it gives you a number, that number might be affected by unknown variables.