I like the sentiment, but remember that every runner is different. If your body can handle 6–7 days of running a week without breaking down then you will be better for it. For the most part I have my runners going 5–6 days a week with 1 cross training (cycling or pool running) day for those going 5. Lifting is also crucial BUT the only way to become a better runner is to run — if you need to cross train it helps but if you can run every day then by all means do it. Running efficiency is so critical over 26.2 and you can’t increase running efficiency on the bike.