I'm considering taking 4 or 5 graduate courses in my first semester. If I choose this route, I won't have any official teaching or research duties due to a fellowship. All of the courses would be math courses and one would be an engineering course. The math courses are real analysis, differentiable manifolds, topics in applied math (mostly multilinear spaces, manifolds, applications to physics), Logic (i.e. axiomatic set theory), and then there is an engineering course. I've seen many of the topics in the real analysis and the set theory course already as an undergrad. Does this sound like overkill? If I had all my time to devote to this, would it be doable?