At 52+ I haven't slowed too much, yet... Back in the day, I was always pretty good, but not real good. PR's are 4:16hs/15:02/31:34 but usually raced around 16:00/33:00. I always ran but not a whole lot, 40-50 mpw. Did a few marathons (2:50:30) but none seriously. Just don't like running that far. Since turning 45 in 2005, I've upped my mileage to 60-70/wk and for the most part, missed very few days and stayed away from injury's.
I've gone 16-oh-something in the 5K each of the past 7 years. Several HM's have been in the high 1:14's. Went 4:50.2 for my only masters mile in 2010 at age 50. Might take another shot at sub-16 this year...but I'm not sure if I really care anymore...
So I guess my key's for Masters success are: Set the bar low, moderate miles when you're younger, double your miles when you're older and stay away from marathons...
Dave