I actually assign 3 types of assignments:
- Written homework assignments
- In class Worksheets
I don't really worry about having a fixed number of assignments per week. I assign them when we are done covering the material. I had a total of 34 assignments over 15 weeks (more than half of those are WeBWorK).
Webwork comes to 2 every 3 weeks. The students will have 3-5 days after being assigned to complete them. Problems are available 2 days after that to allow for extensions.