As a 3DS developer, I announce games when they're in their late beta stage but it doesn't mean I stop working on it.

I stop developing the game 2-3 months before release, so I have enough time to get all the boring stuff done such as age ratings, publishing agreements, lot checking, more contracts, translations, manuals, packaging (if sold non-digitally), marketing, going to game events, testing and more testing, maybe a launch party, etc.

Yes, this is what professional single-person game developers have get through before releasing a single game.