I know you are in the intermediate course now, but have you gone through the beginner's course here as well? You probably know a lot of the stuff in it, but there are a few lessons that have really helpful techniques for getting down new chords. It may be worth at least going through the videos if you haven't already.
I've been doing what you are doing too, and it seems to be helpful. One of the nice things is that it's easily scalable. I'll often switch every other beat for a while, then go back to switching every fourth when I start falling behind.
You'll still want to do the 1 minute timed set once in a while to check your progress.