As a former runner (competitive trackin/xcountry) and a current recreational runner - I cannot imagine never taking a day off is actually safe for your knees and joints. At least for me, I simply cannot run every single day without developing some sort of tendinitis or other mild pain/ache.

Yeah. I'm training for my first official marathon right now and my rest days are sacred. I imagine if it's low volume running it's probably easier, but still, the pain adds up.