Chas Coleridge said: "We had a bike come in for service once that had cranks off at least 20?! I can't remember if it was due to mismatched crank arms or what."
I saw that a lot too. It comes from driving the cotters in in opposite directions, as in when the cranks are horizontal, the nuts are both up. Because of the taper, that will force the cranks to be at the off angle. 10 percent taper per cotter equals 20 percent out of phase.
When you had all the right tools and a good selection of cotters, they weren't so bad to deal with. It just took some practice. The most important tool was something to support the crank arm so you could pound out a damaged cotter. A piece of inch and a half diameter thick walled pipe was the usual tool. The most elegant was a wood block arrangement that supported both cranks and had a hole correctly placed to knock out the left cotter (which was always the one that gave you trouble). The whole idea is to precisely administer some serious brute force directly to the cotter. A quarter inch drift punch and a 2-pound short-handled sledge will take out the most stubborn cotters once the crank arm is properly supported.
The big VAR cotter press was the tool of choice to put them back in. The late Clay Grubic of Tow Path Cycles and Potomac Pedalers in Washington, DC, taught me how to make short work of the toughest cotters. In modern bike shops, the kids who see cotters once a month instead of several times a day are a little astounded at the process.
Earle "I love a heavy hammer used right" Young Madison, Wisconsin