This is an interesting question and one I've kind of wondered myself. I only have ten hubs so far and most were written within about a week. I shifted gears to work on migrating my blog to a new server and revamp it. Now I'm back to writing with the goal of about one article per day switching between HP and my blog fairly evenly.
I've written as many as five articles in a day (once) for a company, but that was a completely different sort of thing.