Are you a contractor or a permanent member of staff? Have you considered doing the alternative as a change? Have you been given the opportunity to lead others technically and or mentor?
Would using your experience and doing technical leadership (not management) interest you? I quite like Team Geek: A Software Developer's Guide to Working Well with Others by Brian W. Fitzpatrick and Ben Collins-Sussman as an gentle intro.
Do you have a path for your career development? Are you doing what you know because it is easy? And finally, when was the last time you took a break/holiday and looked after you (...busting a gut, get home and do more of the same)?
It maybe more appropriate to ask, should I have a portfolio of Java applications/solutions to interesting problems. Learning the pitfalls of a language is undoubtedly useful and I would argue that learning the process of project start-up, testing, maintenance and deployment would perhaps put you in a much more valuable position for learning.