I'll be 45 in May, and this thread provides a little motivation for me to run a sub-5:00 mile this summer.
I haven't raced a mile since an all comers' meet when I was in my early- to mid-20s. But up until I was about 30, I'd sometimes "run to the barn" on the last mile of my 12-14 mile runs in sub-5:00 and as fast as 4:39 three times in a row when I was 29. I've rarely worked out on the track in the last 15 years, but a few years ago, I did 4x1600 and went 5:12 (or 5:08?) on the last one without knocking myself out.
When I give it a shot this summer, it will just be a workout or time trial on the track, and I think I should be well under 5:00. It's just not a big enough deal to find a meet to go to or have it documented in a race. No one cares, except for me, and for me, I don't even care all that much, since I'm not going to approach my PR. I'm more interested in my target trail and road race performances.