Broaden or Deepen...?

Every day I read and learn for 30-40 minutes, and over this year I have refined that habit to try and maximise what I learn (I refer to it as read, write, type), but it just occurred to me that I have never really set a goal for that learning - I just start a new book that looks interesting, and when it’s finished I start another.

I’m now wondering whether I should set an over all goal for next year’s learning (to deepen my knowledge of a subject), or whether the flexibility of just picking up the next interesting book (to broaden my knowledge) is more important.

I’m going to give it a ponder, but I’d be interested to know your thoughts…