I want to get a general feel for how long it takes others to get their respective jobs done.
8 hours 23 minutes and 57 seconds.
Honestly I don't keep track (but probably should!) At a guess, the last one I completed (for the Rocketgirl challenge) took somewhere between 10 and 14 hours over a few days. (Or nights, actually. I don't sleep as much as I should.) That's probably a pretty typical time spent on a piece for me. Still sort of a long time for what it is, but a year ago, my typical time on a similar piece would probably have been about twice as long.
As Kaz says, doing the challenges regularly really increases your speed, as does just drawing and painting a lot. For me, I've gotten comfortable with a fairly regular method of approaching an image, and prepare myself more with sketches before painting in earnest, and have a lot of shortcuts to make life simpler (using layers & adjustments & masks, the warp tool, etc.) -- these things have all combined to increase my working pace.
Another thing that helps me is working on a bunch of things simultaneously, so when I get bored or stuck with one thing, I can just open up something else. Less time noodling that way.
And listening to upbeat music!
Nick AvalloneAngryFungus Art Blog