I've run consistently for the past 30 years, most often in the spirit of the article: long, slow, meditative runs. What my cross country coach in high school called Long Slow Distance ("limber up gentlemen, we'll be doing LSD today!"). Tried a fitbit for a while, found that reducing it to numbers took the joy out of it. I'm back to where I started: no accelerometers or earphones, outdoors, ideally on a trail. I don't go all that fast or do big miles, but it's pretty much where I'm happiest.

About bum knees: I've often been warned that running will ruin them, but I stopped running for two years in my mid-thirties due to work, and then blew out my knee in a frickin' coffee shop, of all places--because the muscles holding it together had weakened from not running. Major surgery, took forever to recover. Limped for well over a year and thought I might never run again. Got a new job and started biking to work--about 4 miles each way. Within a month the limp was gone, a month or so after that I was running again. Been six years and my knee feel great. If you haven't tried gentle cycling and it's an option, you may want to consider it. I think maybe the low-impact nature of cycling let the knee strengthen without being stressed, and once the strength was back, it could handle the stress.