Half of your abstractions are wrong. The hard part is knowing which half.
This is tautological though, it's like saying “starving is much better than eating the wrong food” (for instance: eating quick lime).
Of course you'll always find a way to do things wrong in a way that is costlier than not doing anything.
But also it's very possible to not realise you needed an abstraction until it catches fire in multiple places.
And quite often it's not you that got the codebase to a hundred customers, is it? Sometimes it is a sequence of fresh-faced young developers who didn't have the authority to say "this duplication is bullshit" and were instead compelled to repeat it.
I think a lot of these discussions happen in nice little blog-post vacuums of progressive thinking, where people can go "mmm, object oriented coding obscures intent and clarity, mmm", blog posts with "an X is a Y", "the unreasonable effectiveness of foobar" etc.
In the real world, every duplication that works sticks for good; there is rarely budget to electively replace code that isn't broken. Until one day it doesn't work. And then… how many times is it actually duplicated? How many of the duplicates diverged? How many of these do we no longer need?
So... the wrong abstraction, no matter how bad, is better than code duplication?
> I would go as far as to say that any abstraction you can maintain (that is in active maintenance, I mean) is better than code duplication once you are past a de minimis threshold.
I appear to be in a solid minority thinking this. But I'm OK with it. I'm probably not going to write a blog post.
This blend of opinion is very naive. Every single project is a business requirement away from having the wrong abstraction in place.