As I was looking through my filing cabinet, I came across a folder that I had titled Hybrid Courses. In the summer of 2004 I was involved in a project at my school where we were to describe online learning and develop plans for how it should be accomplished. In my research for this project I cam across a publication by the Australian National Training Authority on blended learning. This can be found at http://pandora.nla.gov.au/tep/45898. While it is somewhat dated, being from 2002, there are still some ideas that are relevant today. I think it's worth taking a look at.

I've always struggled with creating a community of learning in the online part of a class. This powerpoint addresses that and after looking it over, I realize that I'm already doing some of the suggested activities. Yoo hoo!
http://newmedia.unm.edu/common/documents/success-in-the-classroom/valerie-thomas.pdf

I teach at a community college and when a hybrid (or blended) learning class is offered, it needs to follow the usual schedule for the class. The only difference is that there is a shorter time spend face-to-face and then the rest is online. As Susan said above, the length of a class "depends" on the circumstances that the class is offered under.