I know how you feel, my wife is actually the runner, not me, so I would say I mainly do it to support her, and it's kind of fun going on long runs together on the weekends. The problem I have is that I'm kind of heavy for a long distance runner (like 190 lbs), so the miles add up on my feet and knees. I think I'm going to start cutting the miles some and cycling as cross training to spare the joints a little.