I learn what I need in order to achieve my task or solve a problem at hand. So that is the "i know enough" point. And that goes for everything, even my main focus do day to day work. It is good to be aware of some tech/capabilities but learning it only for the sake of learning it is a waste of time as if anything that you do not use, you forget. For example, you can learn 70% of features of a new language you are picking up and that will get you through 99% of your time. There is absolutely no need to learn the remaining 30% of the features that you'll never use.

So in short, learn what you need, but be aware of the options in case you might have a use case for some of them in the future in which case you will know where to look and what to learn.