I've been using 6/bulky yarn to do a design based off of
this pattern, Mel. I changed the pattern a bit because I tended to lose count, for some reason.
So far I've been knitting 3-5 rows (depending on the cowel) and then one with the knit3, yo, k2tog, then another set of just knitted rows. The knitted rows at the beginning and the end seem to provide a better roll to the edges. I'm considering reworking the math on the next one and trying to do the yo/k2tog in a diagonal pattern instead of vertical, if that makes sense. I also have found I only like the pattern in darker colors.
To answer your second question, umm...man. One cowel takes me one round trip drive to LA (so, 6 hours down, 6 hours back), but I can't knit constantly in the car, so I'm gonna guess I probably knitted at max half the time? Maybe less? It's also good for one international flight, ish, because again, I tend to get bored easily on flights when I don't have papers to grade.
So I suppose for its complexity and my tendency to make mistakes because I'm changing the pattern on the fly (and don't tend to write down what I changed), they do knit pretty quickly. And they're a bit more interesting than, oh hey, look....another...scarf.
(Not that scarves aren't absolutely beautiful and lovely and I've made them myself.)