In the Couch-to-5K program, we're currently at an eight-minute run, followed by a five minute walk, then another eight-minute run. Technically, if we were doing the program exactly as written, this run would have only been done once, and the next run would be a full 20 minutes. However, we're going the slow route. There are times when I wish I could improve faster, but I just don't want to get hurt and have to stop. I haven't exercised regularly in a long, long time! Still enjoying the process, though. And everyone I talk to that knows anything about sports fitness...well, the conversation is like:
Me: "We're taking it really slow..."
Them: *nods* "That's absolutely the best way to do it."
I borrowed a book from a runner at work,
The Beginning Runner's Handbook. This version here was published in 1999, and the only thing that seems dated is the advice on water intake. They may have updated it for the new edition. But the thing that jumped out at me was where he says that cardio fitness actually increases faster than the strength of bones, tendons, etc. A person could theoretically run a marathon after 6 months of training, but their bones wouldn't be ready. I think that's good support for the take-it-slow approach.
One final benefit I've noticed...both of us can tell that a morning run is MUCH harder if we eat junk the night before...which gives us that much more motivation to skip the pizza and go with chicken & couscous or similar. :)