I think you might be asking the wrong question. Your stated goal is here: > my primary goal in exercising is to be healthy: to live as long and as > ably/comfortably as I can. My secondary goals are to maintain a > reasonably good weight (preferably BMI < 25) and physique, and to > elevate my mood. I'd back up a little bit and ask the question: *what's the best way for me to achieve that goal in the time I have, which is two hours three days a week*. The walk back and forth is terrific, but the aerobic work you're doing really isn't the best thing for your goals. You currently have a **routine**, but you need a **program**. It might seem like a distinction without a difference, but check a program is very different. Properly designed programs: - Are designed by professional coaches. - Have tens of thousands of successful people backing them up. - Are designed to give you the most results possible in the shortest amount of time. - Will prevent over training. A program is some random collection of various activities one performs that doesn't have any testable results or real theory behind it. Lots of people have routines, effective people have programs. Regarding your BMI, grams come off at the gym and pounds come off in the kitchen. So regarding your bodyfat, you need to focus on the nutritional component. [And strength training has been shown to generally have a more profound effect on weight loss than aerobic activity anyway][1]. Regarding your longevity, there is a lot of evidence in favor of free-weight strength training when it comes to bone density, balance, connective tissue toughness, and hormonal balance. Even neural pathways get better defined. I would take a full overhaul of your fitness activities and give something like Starting Strength a spin. Coupled with good nutrition, I don't think anyone can argue that there's a more balanced way to achieve overall physical fitness for a novice. [1]: http://fitness.stackexchange.com/questions/19114/aerobic-vs-anaerobic-for-better-fat-loss/19117#19117