I've come to the conclusion that there's not much reason to do long, slow cardio unless you're training to be an endurance athlete. This is coming from a guy who used to run around 40 miles a week. I enjoyed it but I didn't enjoy being small and weak. Funny thing is, I've put on very little fat even while all-out bulking, as long as I do my part in the gym. And even though I've done almost no cardio (outside of my job) for over a year, the couple times I have run I was surprised to find that I hadn't lost much aerobic capacity at all. Yeah, I can't run a 4:56 mile like I could in high school, but who cares? When is that useful in daily life? I have to lift heavy stuff all the time, though. Strength is just more useful. When I do decide to incorporate some cardio, it will be HIIT or something similar.