Are you doing this for personal growth/satisfaction/enrichment? If so, more power to you. I'm personally more inclined to read a (non textbook) book or watch sports during my free time, but if that's what you enjoy then good for you.

Or are you doing this to maximize earning potential? If so, to me (maybe not to you) that's wasted time, unless you're banking over (arbitrary figure) something like $750,000 or more yearly.