well I usually take about a month from first sketch to finished product, but I tend to work on 2-3 projects at the same time, rotating between them. I do this partly because I find myself going stagnant if I stare at the same model too long. Then again, as I learned from writing classes. I like to put the model away for a bit then re-look at it to see if there are any improvements I can come up with. Then again some things are still on the hard drive waiing for me to get back to them. 

I find that tweaking the produc to work well in poser is the most fustrating part of the job. While, for me, textureing takes the longest time.

mike