Learning a new tool when you have limited set of current tools is a good investment. But there is a aspect of marginal returns that comes into play here. It's

Learning a new tool when you have limited set of current tools is a good investment. But there is a aspect of marginal returns that comes into play here. It's not just the increased demands on your time, but the knowledge that it's ticking away... As you get older you get more critical/anxious about wasting time and more reticent about investing in something that has no compelling return on investment.