How much time should you spend automating a routine task?

Today's XKCD really tickles me. "Is It Worth the Time?" is a handy chart showing how much time you can invest in automating any recurring task in order to save time, on balance, over five years. I am an inveterate automator of recurring task, always looking for ways to shave seconds.

On the other hand, I think I'd halve the figures Randy gives in this chart, because many of the routine tasks you automate will change in some significant way in less than five years and require further work. Also, the chart fails to account for the losses in innovation and serendipity you suffer when you over-optimize a routine task so that you effectively can only do it in one highly constrained way.

Finally, there's the opportunity cost of clearing a relatively scarce large block of time to spend on automation, which may be a better bargain than giving the task more time overall, where that time comes out of a pool of more abundant small snips of time.

In other words, a five day block of time given to automating a task might cost more (that is, might crowd out more productive work) than ten half-day blocks of time or 40 one-hour blocks.

Still: this is crack for me.

Is It Worth the Time?