My own concept is rather simpler I would say: apply the 80-20 rule; that is, 80% of your time, use the tool set you know best that get you paid and the remainder 20%, invest it in learning things that interest you.

Of course, when it's off or weekend days, feel free to swap the rule to 80% learning and 20% to anything else you must do.

Obviously it's just a suggestion, not a mandatory task, but hey; whatever works for you, isn't that right?