I go back and forth. Several times I've spent months during which I've found a way to fit in many hours of exercise a week. But then it gets cold (and, worse, dark—and worse yet, slippery) and I find it easier to just stay home and read a book. And, as I said, when I am exercising a lot I find it easy to let the time spent exercising get out of control to the upside—I exercise so much that it becomes hard to fit in all the necessary household tasks.

So, I was looking for some sort of target. I think an hour a day will work fine. If I'm getting less than that, I need to do more. If I find that I'm getting more than that, I'll probably benefit from finding a way to be more efficient—cut back some junk miles in favor of a longer endurance run or some faster speedwork.