Laurie Sullivan at SearchBlog (MediaPost) published an article discussing conversion findings by NetElixer. It contains some fascinating data that I recommend checking out if you are interested in understanding when people convert in the online shopping space.
However, I would caution you that the data varies greatly depending on the industry. I also believe that most people do a significant amount of browsing and shopping at work, based upon some baseline data collected from some of my own clients.
Regardless of your industry, you can do some simple day parting with Google Analytics. Look at when people are converting to minimize your planned outages, maximize customer support windows and to better understand your customers.