Batman has just received a terminal diagnosis. He will die in one year and nothing can save him.
Worse, all costumed heroes and sidekicks immediately abandon him. He cannot appoint a successor and cannot rely on any other costumed superhero after his death - nobody else is going to step in or step up to protect Gotham. Alfred is still capable of impersonating him to an extent but can't be trained as an actual Batman. No help whatsoever from Robin, the rest of the bat-family, Superman, etc - he's on his own.
He will still stick to his morals and will not kill or permanently injure any of his enemies.
Using plans and preparation and scheming, how long can he maintain Gotham's stability and keep his opponents in check after he dies?
(Assume that the Joker will continue to be the threat he usually is when Batman is alive, and will not go catatonic or become a normal person once Batman is dead the way he sometimes does in some continuities.)