I am planning a new course for the spring of '13 that I think will be TBL format.  Its a biology course for non-majors, with a weekly lab.  The course will be structured into 4-5 modules over the course of the semester.  I am considering how to set up the class sessions - formally I will have designated "lecture" and "lab" times on the schedule, although I am considering at least partly abandoning that distinction in practice and using some of the "lecture" for lab activities and some of the lab times for extended applications.  But in designing this course and thinking about the schedule, I am looking for advice about meeting 3x per week (55 minutes MWF) for "lecture" vs meeting 2x per week (80 minutes TuTh).