Considering we shot in Feb and LR 4.0 wasn't released when we shot, I think we've done a good job of being timely...note, we'll be shooting more videos in early June (prolly not to be released until end of summer) to pick up the new stuff in LR4.1 and pick up some additional stuff we couldn't shoot in Mexico.
If you think this stuff has been slow to be released, I suspect you've never cut video? Chris has done an outstanding job of getting stuff cut and released. While Mike and I can spend a few days shooting this stuff, it's really up to the editor to make it comprehensible...which Chris does a great job at. Could he work faster? I suppose...but he does want to have a personal life (and deserves one).
I googled the "Rory Approved Frequency of Video Releases" and could not find reference to such a standard. Maybe if you could publish it here, all future releases could comply.
I think that the releases are plenty fast considering the quality of the video editing as well as the quality of the content. Besides, when I purchased the series, I was fully aware that more videos were to come in the future. There are over 5 hours of video at the moment. I feel that the price I paid was a very good price for over 5 hours of video...but there is lots more to come, so I have nothing to complain about! I am stoked.
The OP wanted to know whether to get the video or buy a book. The videos are great but you do not have to wait months to see each chapter when you buy the book. This is not a criticism of LL, merely an observation about the medium.