When I'm designing dials for equipment, I often need to place a dash at a given number of/angular intervals around a curve (eg, ten 1mm dashes around an arc of radius 15mm and theta 3pi/5 radians). Often the simplest, most time-effective way to do this is with dashed lines.

Currently, in order to work out accurate gap spacings without dashes getting cut off at the end stops, I end up having to calculate arc lengths and gap spacing by hand. I daresay the math is good for my brain, but it would be really handy to input "dash width: 1mm, number of dashes: 10" and let Illustrator work out gap spacing for itself.

This would be useful for straight lines, too — while it's possible to copy/paste objects and distribute them across the length of a placeholder rectangle, it would be a great deal more elegant to solve this with dashes.