I think it depends on what i am working on...but when it comes to nice pieces, probably a week and then some.
I take forever trying to make things perfect. and seeing as i only have either after work or before work and the weekend to work on something, things can drag. i can spend hours trying to make one bit perfect. i think i take too long. just need to work smarter i guess.

depends on how i've been thinking about it and if i have a deadline. things with deadlines usually take somewhere between 3 hours to 2 days.

Depends on the piece, and on my schedule

Most usually pieces will very between 4-7 hours, but there are some that take 10+ hours (those I usually play with an hour at a time for a few days, sometimes weeks).

It depends on the piece, really. More detailed ones take longer, simpler ones don't take as long... but roughly a work day? A little more? I guess it also depends on the size of it. I've worked on large pieces in traditional media that I had to work on over the course of days/weeks, but I didn't work on them all day due to other obligations.

Comics work has trained me to think that if I'm spending more than a full day on a single page, I'm working too slow or over-working the piece and probably sapping it of is vitality and dynamism. Not necessarily true of every piece, of course, but I really want to train myself to work fast as a point of professional necessity.

Also, I get impatient and fear I'll never finish a piece if I take too long. I admit, I'm a bit of an attention hound, and I can't wait to post my work online... :/

around 3-6 hours but that's cuz I just draw faces and rarely bother drawing the whole body\background..etc orz I wish I could have your determination in finishing artworks

Most of my projects take over a year.
Because I'm a lazy motherfucker and don't usually take any art classes.

What do you mean by "producing" the art? You mean uploading it to DA.

About 1 hour. I do get bored easily.

I do know that when you get in the zone and things start working for you, time seems to run at double speed and before you know it, it's like 2AM or something! aargh!