Three call sites is when the shape becomes visible.
[ trace // field response ]
Beginners are taught not to copy and paste. Experienced engineers do it on purpose, because three or four call sites of the same shape reveal more about the right abstraction than one site ever could.
Refactor when the duplication starts to hurt — when changing one site implies you should have changed three. Until then, the duplication is reconnaissance.
Premature DRY is more expensive than late DRY. Copy first; abstract once the shape is undeniable.
