I've made the decision to "brownfield" many projects. My GH[0] is full of archived, and even private, repos that I no longer maintain. I have retired most of the apps that I've written. I only have a few left on the App Store[1].
I do make sure to explicitly "freeze" a project that I'm no longer maintaining, and indicate such, in the README. I hate encountering abandonware that is only obvious, because of the last modified date.
But the projects that I do want to finish, I make sure to do a "full-fat" job. If I consider it "done," then it gets the Full Monty. I also continue to maintain. If I can't do that, it gets archived; even if I had completed and shipped it.
Those are valid questions, but I don't usually get that exacting. The projects that I walk away from, are usually because they were just for learning, I got into a "death spiral," or that were eclipsed by something else.
> I hate encountering abandonware that is only obvious, because of the last modified date.
The date plus hundreds of issues, of which the last dozen are unaddressed variations of “is this project still alive”. And then you check the creator’s account and they’ve been active on other things. Just archive the repo. Please. It’s fine if you don’t want to work on the project anymore, that’s 100% your decision and your right, and no one should be able to criticise you for it. But please just do the tiny courtesy of letting other people know so an alternative can crop up and flourish. Archiving a repo takes less than a minute and is reversible if you ever change your mind.