There was recently some discussion on how many minutes callers typically run a contra dance, with a lot of "well, it depends" answers. There's a place for that, but I think it's also helpful to have some numbers. I went back over the last ten evenings where I have recordings:

It looks like 8-9min is pretty common. How much variability is there within an evening?

Most callers stayed between 6.5min and 12.5min: one ran two dances shorter than that; another ran eight longer (in two evenings). If you're going to run dances much over or under 8-9min it's good to warn the band so they can plan.

These were all 3hr evenings, and the callers called 8-12 dances. Two of the evenings with 12 dances had a square: those were shorter (4:51, 4:59) and I didn't count them above. This makes 2/106 squares, well down from 14/19 in 1965. Including the squares, here's the relationship between number of dances and dance length, inversely proportional as you'd expect: