It really depends on what I write about. I try to stick with topics that I have a high interest in and also have a great deal of knowledge about. My average Hub takes approximately (I never really timed myself) 2 - 3 hours.
I will usually blow through the entire hub quickly and get a good outline completed and then go back and do my editing to make it more visually (and gramatically) appealing.
My topics are rather limited and I have always stayed within my comfort zone, so I have also slowed down quite a bit from when I first started.
I follow a few Hubbers that publish 4-5 Hubs per day which amazes me because they are very high quality hubs.