How Long Does a Usability Study Take from Start to Finish?

This question will likely have no single correct answer, but I'm looking for personal estimates on how long it takes you to complete a usability study from start to finish, including research, writing the plan, recruiting users, conducting the tests, and analyzing/reporting the data.

I've read a number of articles on the web (this one seems to have the most science behind it: Cost of User Testing a Website, but I'm looking for your input based on your own experience with usability testing.