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Your documentation will tell when you need an abstraction. Where there is something relevant to document, there is a relevant abstraction. If its not worth documenting, it is not worth abstracting. Of course, the hard part is determining what is actually relevant to document.

The good news is that programmers generally hate writing documentation and will avoid it to the greatest extent possible, so if one is able to overcome that friction to start writing documentation, it is probably worthwhile.

Thus we can sum the rule of thumb up to: If you have already started writing documentation for something, you are ready for an abstraction in your code.