What about the effects of 'time spent on the problem' (ie compounding)? If you are only learning for learning sake, then getting to a "101" or "102" or "103" (to use American college level terminology)is fine I would assume. This might take 1-3 years of learning/study/doing.
But if you truly want to "master" something - then does "constantly thinking about problems" mean you will never benefit from the same 'compounding' effect as someone who has spent 3/5/10 years of their time on that problem?
Or - is all your "need for cognition" - mostly in one domain space (e.g. "Computer Science" or "database structure" etc)?