I’ve been thinking, and I’ve come to the conclusion that I’ve cared too much about what happens to John post-Reichenbach and not enough about Sherlock. I think that, if Sherlock was gone for 3 years, John could adapt. He would still have Mrs. Hudson and Lestrade and eventually Mary and he would be able to slowly ease himself back into the real world. He would start to work again, he would make new friends. His vivid memories of Sherlock and their partnership would linger but they wouldn’t be the only thing he’d think about anymore. John would move on with his life. Slowly, but steadily, Sherlock would only become a distant memory and pang of lost friendship.
But for Sherlock, it would be completely different; he would be back to square one. He’d be thrown out there into the world without the person he had grown to known as his only friend. He wouldn’t have anyone; not even Mycroft, his own family. The world would once again become a throng of unfamiliar, unwelcoming faces and John wouldn’t be there as his miraculous conductor of light to help guide his way through it all.
So what would Sherlock do?
He lasts three years. Three years alone.
Three years without his army doctor, or anyone else.