I'm a high-mileage runner and I replace my shoes every 400-450 miles. I use a combination of both mileage and feel. If I notice a significant decrease in cushioning or support, I'll replace them, regardless of the mileage. Better safe than sorry, especially with the high risk of injuries.
I've tried yoga a few times, but I still think it's overhyped. I've seen no tangible benefits to my running performance. If you're already doing strength training and proper warm-ups/cool-downs, I don't think yoga adds much. Maybe it's just a nice way to relax, but I'd rather spend my time on actual running.
Agree on keeping it simple. Water bottle belt and good socks are essentials. Don't need all the bells and whistles. Focus on training, not fancy gear.
Finally some decent Olympic coverage, but why do they always focus on the flashy relays and neglect the grueling individual events?