It would depend on how many custom pages/page templates were required, but it usually only takes a few hours to create the required screens to send for approval in photoshop.
A. e-commerce site with an average of 6 template components -
7 hours B. Information/branding site – 4 hours to create the over all theme and all of the required styling elements C. Heavy content magazine type blog site – 4 hours
Again this is just a rough idea and it can vary greatly depending on how detailed the brief is, the existing brand you have to work with (if any) and a whole heap of other variables!
Even at equal skill levels and efficiency most people have their own styles/approaches.
eCommerce definitely takes the most time for me. Researching or thinking strongly about usability and call to actions etc.
I would say average sites, I quote anywhere between 6-20 hours depending on the usual budget/deadline variables. The days where I need to sacrifice a goat or two for inspiration can tack on a few extra.
Never missed a deadline yet, *dances ritualistically*.
I don’t think you can really accurately answer this question. Another way to put it is that I really don’t think there is a *common* time. Really depends on how the designer works. Some people create only 1 design from the comments of the client. Others design 2-4 renditions to provide options. And there’s a lot in between.