Sounds good, but it's to that easy to fit it all in in a normal week, and so there will always be a compromise. Plus, I actually quite enjoy doing a little bit of running. So my main approach, as you know, is to do intervals. I run for either a set time or a set distance and I slow down, usually to a brisk walk for the low intensity intervals. It's mostly random because I don't carry a stopwatch with me, although I do have one that can be set to time intervals. In the end I rely on a number of things.
For time, I tend to have Runkeeper to tell me what I'm doing every 5 minutes. Polar Beat tells me every Km, if I'm using distance. These are great for even intervals, but for something a bit more random I often use lampposts, telegraph poles or even bus stops. I also work on the principle of running when I feel like running and not running when I don't. I'm not training for a 10K or marathon, so if I don't feel like running I have no need to run. It's pretty obvious that there is a physiological benefit to running over walking the same distance. You work your heart and lungs harder, your muscles have to be more efficient, as does your whole cv system. But a healthy cvs doesn't require that you do anything much more than moderate exercise for 30 minutes a day five days a week. I've tried to include an element of running in my training schedule only because I want to get fitter not just healthier.
Here's the data, for example, from my most recent 7Km session:
The red line is heart rate and the blue line pace. You can see that the intervals vary, and interesting to see how a couple of times my heart rate peaked just as I was coming to the end of an interval. For me, I think this is a good session because it pushes my hurt rate and recovers before going again. This, in theory, should improve my sprint speed and recovery.
So when you see bits of data about me running or even walking a given distance, it's invariably true that it's a mixture of both. Occasionally I'll run all the way just to prove to myself that I can. It's a bit of a fitness test and psychological test too. When I run, the first 100m or so can often feel like my lungs are going to burst, but once I settle into a rhythm and take control of my breathing, I find a manageable pace and away I go. Exactly how far I could maintain this pace I don't know. I do know I can run 5Km without stopping, and I'm guessing that stubbornness might just carry me another kilometre or two. One day I might try it.