The assumption that a little more focus on one particular thing will make one a specialist. To become a specialist or a master you not only need undivided attention but a natural flair for it. You can practice music all your life and still not compose like Mozart or Bach.Or even someone like Jiro Ono(http://www.thedailybeast.com/articles/2012/03/11/jiro-ono-co...). Most of us will never become Masters, being no more than experienced hacks. That doesn't mean one shouldn't target for it. "Stretching oneself too thin" is a common refrain among technologists implying that if they rather focus on one skill, they are bound to become Masters. In my opinion it's as much about serendipity as it's about perseverance.

"Master" is a bit of a baroque moniker. Can we agree that a "master" ought to be much further along than a "specialist?" i.e. the Java master should understand byte code and personally know folks of the original Sun Java team?

Otherwise it just sounds like I can become a Javascript Master in a few months.

I prefer the phrase "experienced in x". In my opinion specialist and master should have the same weight. Calling someone "specialist" can be a misnomer for a master if the scale for measurement is not agreed upon.