This may be down to a matter of opinion. In which case, feel free to downvote/close the question.
I've been looking for a word for ages: A word that fits the concept of "only do something once, and only when it is needed"
I still didn't find the word, so awarded a bounty. Now I have 2 answers suggesting the same word. One was quicker (with sufficient explanation), one was answered a little later, but with a more elaborate example of how it could be applied.
Who should get the answer reps?
I wouldn't usually ask, but since there's a 100 bounty on it, I'd prefer to get it right.