That's what I'm finding. I started with one course because I was worried about time to study and time with my wife and child, but now I'm thinking I could do 2 courses probably without too much concern.
My only worry is the Math course. Not having gone to University or high school in 20 years I'm fearful. The other courses have been easy so far though, but like you I'm working on the field, so it's not so new to me.