Writing on more than one novel at a time

I've got a good percent of Heir to Magic copied over into yWriter, but I have shifted my focus to another story for a brief time. There is a good reason for that, the other story works better at the point I am at in going back over the writing course I have been taking.

So, I am sort of pinging between the two novels at the moment, working on both of them as the muses shift their focus from just wanting to write, to working on the course work. It seems to be working so far, especially since I have kind of a gerbil mind that likes to shift focus at random points between one thing and another.

I'm not sure how many other writers work well when they are focusing on more than one novel at a time, but I think it would be interesting to look into as a study to see if some writers can function better when they are working on several novels or if the same group works better focusing on only one novel at a time.