> On March 7, 2019, all Google+ APIs and Google+ Sign-in will be shut down completely. This will be a progressive shutdown beginning in late January, with calls to these APIs starting to intermittently fail as early as January 28, 2019.
If you are asking how to responsibly shut down an API, that is a hard thing to do. Having the API start failing intermittently a bit more than a month after you announce it won't be supported any longer is definitely not the right way to do it though. Giving people plenty of advanced warning is the least you can do, even if you technically _can_ shutdown the API whenever you feel like it.
I think it makes perfect sense. It makes teams that didn't get the shutdown notice aware of it in an acute way and encourages them to take action without putting them on the spot.