Depends on the speed of your connection, but pulling an Windows OS image with all the drivers and factory supplied apps can easily take several hours.
Starting from the Win 7 image on a "restore partition" it has taken me 4-6 hours over a 3G wireless connection just to pull the updates, but since it catches a Service Pack, that usually means almost a whole new Windows.
With DataSafe, you are also dealing with whatever bandwidth is available to the DataSafe server. I have no experience with that one, but have worked with other external storage sites that I find much slower than the download servers for Windows updates.
Tom Test
Itasca Spirit 29B