This actually made sense when I thought about it. When I have plenty of time, I'm probably not doing much in life outside my normal routine, so there is nothing new to inspire topics. When I'm super busy that means I'm doing things, going places, and seeing people that I don't normally see, which is more likely to spark a blog idea. To have new blog content it's best to experience new things.
Happy Saturday. Go out and do something blog worthy ;-)