Isbjorn It seems like you're using the Software Center to try to update. Might I suggest trying to update via the Terminal application and see if that produces any issues or errors so we might better see what's going on.
Open a Terminal and type sudo eopkg up
and press ENTER, then type in your password and hit ENTER again to allow the system to update. It may take a minute or two, but it shouldn't take "hours" to update unless maybe your internet connection is not very speedy. Give that a try and let us know if that helps at all!