Just to add another data point for you, I’m about to turn 46, 5’10”, 185#. I am currently at about an 8:30/mile pace running outdoors. This morning was 33:53 for 4 miles. I have run a lot since 2008, and I used to be quite a bit faster. 10 years ago I ran our little town 4-mile race in 28:00 flat, but there’s no realistic way I could get back anywhere close to that. I’m pretty sure that I can still do a single mile in under 7, probably closer to 6, but I haven’t tried in a while. I’m not trying to be the fastest guy in the world, I just try to maintain some decent cardio health and I’ve grow to enjoy running, in a way. It gives me a little time to think before the day starts. I used to run 5-7 days/week, but now I keep it to 3 and mix in some weight lifting. I’ve never had any knee or joint issues, but I think more about that possibility as I get older.