Ran 7.5 miles in about 55 mins 2 weeks ago. I typically run 4 miles 3 times a week. I'm not a speedster, usually only aim for 7 minute miles or so. Been running this way for about 16 years, knees still good. Key is changing your running shoes very frequently. I do the mountain biking thing occasionally, but it's just quicker and more convenient to go for a 30 minute run.