My bike computer has a max-speed reading, and I usually take a glance at the highest speed I've managed on my faster rides. No, it isn't important in the grand scheme of things, but I'm mildly curious.
I did a long and very hilly ride 2 weeks ago, and at 3 separate points, I saw 50mph go by on the computer - for the fraction of a second that I could tear my eyes away from the road. Although I've never measured it, I don't think I have the gearing to pedal much faster than about 47 mph (50 x 12) - so at those speeds I was free wheeling, head down, ass up, elbows in, and knees clinching the top tube.
One road in particular was wide, perfectly surfaced, straight as an arrow for about a mile and a half, had no traffic, and seemed so steep that I felt I was going down a mine shaft. Scary as s**t, but exhilarating I saw 50mph go by, and kept accelerating - but did not (could not) take another look until well after I'd slowed down, halfway up the next hill.
When I got home, I checked the max speed reading: 59.5.
(I'm sure I exceeded those speeds when I was in my late teens / early 20s, and my racing buddy and I used to sneak onto a section of the Interstate, catch a draft from trucks as they lumbered up a hill, then overtake them on the way down. We used to thrash really long gearing in those days. But I couldn't say what speeds we did with any confidence.)
I'll be curious to know what speeds you've picked up.