For me, I was just a student writer, so I completed an article roughly once every two weeks. The first phase of every article was research. Whether it was reading into a new technology, a start-up company, or sometimes interviewing industry professionals.
After gathering data and research, I would compose the article, make edits, perhaps find relevant pictures, etc. I'm not entirely sure how many hours/week I would devote to articles, as sometimes the research and writing came easier for certain topics than others.