I started to get decent traffic from them at 8 months, but I didn't start writing more than a few hubs until I was on here for awhile. It may be faster for you since I was so slow at getting anything done.
It all really depends on what you write about. Be sure to use Google's Keyword Tool and that you are using good keywords. Then check the Google search engine to make sure millions of good pages haven't already been written about the topic.
Next be sure to get some links to your hubs and you should start doing well. PS. I only make about $50 a month still. Some people earn a lot more.