But it should be a lifetime activity. All game programmers must learn new skills all the time. It is the only way to keep up with technology. Every game programmer's goal should be to catch up with technology. It is an unreachable goal.
Technology is a moving target.
As soon as you get close to it, it changes again. But that is what makes this industry so dynamic, and so full of opportunities. Choose some aspect of technology that interests you, and aim for it. Let your personal interests guide your career. It will only result in an inferior game.