"Master" is a very strong word.

Why "Master" something that you are not using?

My experience has always shown that there is an ongoing process of learning in anything. Requirements will guide you to greater "mastery" of something you have already been exposed to; But if you limit what you are exposed too, then you might miss out on a better tool for a particular problem.

IMHO Keep exposing yourself, "Mastery" will rarely come but greater learning will come naturally as neccessary.
Specialization is for insects.