- It's going to be done many times (so it'll save time), or
- It needs to be done exactly the same each time
Interestingly, the Braidy Tester points out there's another important reason to automate, one that - as a developer - we invoke all the time: Morale. Even if I'm only going to do something once, if it doesn't take me much longer to automate it, then I will, for the sake of my own sanity. I'm a developer, not a computer.
It's worth factoring in the 'hidden cost' of not automating when making leadership calls, and err on the side of automation when it's a close call. Is not automating worth the morale cost of making people do really boring work?