> I think a thing is not a good example though — takes longer than a few hours / an afternoon, to write a thing, add tests, fix bugs, corner cases. More like a week, or weeks, ...

You're making my point for me. This is exactly what I meant by the lifetime of support you're signing up for by writing lines of code. Once you write that code, you're now in the business of supporting that code. Was that a good decision for your business?