What to Work on Next?

A question that has my brain spinning slowly, but still slowly.  I still have a number of books in my head, but I don't know how many years I have left to complete them.  I have been planning three books on Elizabethan literature--my academic specialty--and a book on the nature of God, defending Christianity. I've been working on these for years, adding a bit to them each year.  Since more research is required for such books than for fiction, these take me longer to work on.  Besides, writing fiction is more fun  and I give more time to it.. Moreover, I'd like to write an introductory book on Shakespeare for the general reader. Of course, a number of these are out, but I'd like to do one just for the fun of doing so and to share some of my knowledge about my lifelong specialty.  Moreover, I have several novels written in long hand before computer days that I would still like to publish, as well as several unwritten ones in my head.  I spent the winter adding to my planned nonfiction works.  I plan continuing to do so through the spring, but also want to resurrect one of my early completed novels from the early sixties.  Sometimes I wish I could had a machine that would allow me to slip periodically into another dimension where time did not exist, so I could get all these planned works done.