I ran track in 9th grade (1967), but only because I was a nerd and wanted to get a better grade ('A') in PE since the school district included PE classes when computing GPA. Ran a 220 leg in the medley relay. Also ran the mile in one meet and managed a 5:10.
Didn't really run again until 1974 when I started grad school at Stanford. There was a group of faculty and grad student runners there called the Angel Field Ancients and I did some casual running with them on campus, in the foothills, on the Angel Field track, and occasionally in the Stanford stadium for time trials (best mile was a 4:49). One day a friend mentioned he was go to run Boston marathon and I said, "Gee. I'd like to run a marathon, too.". He asked the telling question "Have you ever run a 10K or other race?" and I replied in the negative. He suggested that it would be a wise move to try a shorter race first. I upped my training and 2 years later did a 20 miler in just under 2 hours.
I ran my first marathon, Avenue of the Giants, in 1979 in 2:43:23. The next year I ran Boston and one other marathon. In 1981 I ran my first trail marathon, Pike's Peak (~7000 ft climb and 7000 ft descent) plus 3 road marathons. The next year 8 marathons and, on the day after Christmas, my first road 50 miler in ~6:50. In 1983, at age 30, 8 marathons and a trail 50 miler. 1985 brought a new challenge with my first trail 100 miler, the Western States Endurance Run, plus 2 fifty milers and 9 marathons.
The racing schedule went on until May 1991 when life sort of hit the fan as my wife and I both began telecommuting and traveling for our jobs, while at same time we were establishing a farm and building a house in a new community. I basically went cold turkey on running until about 2004 when, at age 52, I picked up casual training again. In 2006 I ran my first road marathon in 15 years with a time of 3:24:44. I also did 4 trail 50Ks and flat 50 mile run in 7:21:10.
I continued running races through 2011 with one more marathon, numerous 50Ks, four 100K's, one trail 100 miler - Bighorn in 2008 at age 55, and three 24 hour runs of 117 miles in 2008, 119.5 miles (2009), and 112 miles (2010, at age 57).
My total racing mileage from 1978 to 2011 is 6394 miles (10,291 kilometers) at an average pace of 9:17 per mile. Of my ~100 marathons, 35 were under 3 hours, with a personal best of 2:40:39. My best 100 mile time is 18:16 in 2009 as a split in a 24 hour at age 56. My best 100 mile finish was a 9th place at Western States.
My running interest now is unsupported adventure runs with small groups of friends (3-5 people) in interesting locations. These runs include circumnavigation Mount St Helens in Washington (~45 miles), a Grand Canyon double crossing (South rim to North rim to South rim, ~42 miles, lots of uphill), 3 days of running in Zion National Park, and just last week, 5 days of trail running around Sedona AZ. The pace is slow, the company is great, and the scenery is spectacular.
I too anticipate running into my 70's.
I hope you continue to enjoy the benefits of running. Someday, out on the trail, years from now, perhaps we will pass and share a mutual thumbs up.