[elchief]

Well, you need to know what is out there, and what is possible. So at least skim over some of the technologies. You could waste a lot of time if you didn't know say, Sass, existed.

There's also a timing problem. If you invest now, and learn technology T, then when you are in the middle of developing a project, the marginal cost of using T is very low. But if you are up to your neck in a project, and then need to take a week off to learn T, you are not likely to do so.

Personally, when re-starting my tech career I wish I had learned Java (or any JVM language) over PHP, PostgreSQL over MySQL, and Dojo over JQuery.