Why would Dumbledore say "After all this time?" to Snape?

Question

When Snape's changed his allegiance from Voldemort to Dumbledore he did so expressly because he wanted to honour Lily's memory by protecting Harry. It was Dumbledore himself who persuaded him to take this course of action.

“If you loved Lily Evans, if you truly loved her, then your way forward is clear.”
Snape seemed to peer through a haze of pain, and Dumbledore’s words appeared to take a long time to reach him.
“What — what do you mean?”
“You know how and why she died. Make sure it was not in vain. Help me protect Lily’s son.”
_{(Deathly Hallows, Chapter 33, The Prince's Tale).}

If this was the basis on which Snape changed sides and the basis for Dumbledore's trust of Snape then why on earth would he be surprised, 15 years later, that Snape's motivations remain the same? Dumbledore seems genuinely surprised that Snape is still acting out of his love for Lily. He is confident that telling Snape that Harry must die won't cause him disquiet. He questions why Snape's motivations would be unchanged "after all this time".

[Snape] stood up. “You have used me.”
“Meaning?”
“I have spied for you and lied for you, put myself in mortal danger for you. Everything was supposed to be to keep Lily Potter’s son safe. Now you tell me you have been raising him like a pig for slaughter-”
“But this is touching, Severus,” said Dumbledore seriously. “Have you grown to care for the boy, after all?”
“For him?” shouted Snape. “Expecto Patronum!”
From the tip of his wand burst the silver doe: she landed on the office floor, bounded once across the office, and soared out of the window. Dumbledore watched her fly away, and as her silvery glow faded he turned back to Snape, and his eyes were full of tears.
“After all this time?”
“Always,” said Snape.
_{(Deathly Hallows, Chapter 33, The Prince's Tale).}

Bear in mind both that:

• Dumbledore was completely confident in Snape's loyalty. He trusted him implicitly and absolutely.
• The sole basis for Snape's loyalty, based on what Snape actually revealed to Dumbledore, was his commitment to protect Harry on Lily's behalf.

Why does Dumbledore suddenly cast doubt on Snape's commitment to honouring Lily and protecting Harry here? Surely that was the basis for his allegiance to the Order all along? Doesn't Dumbledore's absolute trust of Snape imply that he was completely confident that Snape's motivations were unchanged?

Answer 1

He's not referring to the commitment to the Order - he's referring to the Patronus, and what it represents.

If the person you love has an animal form, your patronus can turn into something resembling them.

Tonk's patronus became a wolf after she fell in love with Lupin.

As Harry swung the cloak back over himself, she waved her wand; an immense silvery four-legged creature erupted from it and streaked off into the darkness.

_{^{Chapter: Snape Victorious, Harry Potter and the Half-Blood Prince}}

This was a definite change, as Snape points out to her shortly afterwards (while being his usual prick self).

And incidentally," said Snape, standing back to allow Harry to pass him, "I was interested to see your new Patronus."

[...]

"I think you were better off with the old one," said Snape, the malice in his voice unmistakable. "The new one looks weak."

_{^{Chapter: Snape Victorious, Harry Potter and the Half-Blood Prince}}

Lily's patronus was a doe - either coincidentally or specifically because of James' Animagus form (probably the latter).

You can't choose your Patronus. The fact that Snape's is a doe - is Lily - means that he still truly loves her, and that his feelings for her haven't weakened over the years. It's the depths of this love that hits Dumbledore so hard - that's the reason he gets tears in his eyes on seeing the Patronus.

By "After all this time?" he means "After all this time your feelings for her haven't changed, or dimmed, or faded?"

Answer 2

It's been almost 17 years since Lily died, and about 22 since Snape was rejected by Lily in fifth year after O.W.Ls.

Patronuses change after a great shock, and emotional upheaval (from HP6):

“Tonks’s Patronus has changed its form,” he told him. “Snape said so anyway. I didn’t know that could happen. Why would your Patronus change?” Lupin took his time chewing his turkey and swallowing before saying slowly, “Sometimes . . . a great shock . . . an emotional upheaval . . .”

It's not normal to be in shock for 17 years after a breakup, or to still be in love enough for a Patronus after so much time. Obviously Patronuses revert back to original form once some of the grief of the loss has worn off.

He's not saying "after all this time, you still have a reason to be loyal to me?" he's saying "after all this time, you grieve for Lily Potter?"

Answer 3

I think the context of the

“After all this time?”

is set by the preceeding:

“But this is touching, Severus,” said Dumbledore seriously. “Have you grown to care for the boy, after all?”.

And what that means is simple: Dumbledore asks if Snape finally gotten over his dislike of Harry. I'd say that saying that Snape was not fond of the boy is an understatement of highest caliber. All that matters to Snape is what Harry represents - a part of Lily that's still here. But it's the only thing that matters to Snape, really.

I do not precisely remember the scene from the movie, but i think Rickman then has very unmistakable expression on his face... Which tells a lot, especially since that bit is missing in the book. Then again, JKR was consulting of the movies, so...

So the question is much less an accusation or castigation of any doubt by Dumbledore, but genuine surprise at the strength of the Snape's feelings for Lily.

The surprise may be explained by the nature of the Patronus charm: always an animal, it expresses the nature of the caster, is linked to significant events in one's life and with requirement for a single, very happy memory.

Think on it for a bit and it's possible that Snape was very happy being extremely unhappy. Sort of creepy.

Answer 4

Snape make a bad break in this conversation. He calls Lily by the surname, says "Lily Potter." In my opinion, this is not an accident, something that Severus began to perceive her not as Lily Evans, but as Lily Potter, says that he accept her along with her husband and child.

But here we are resting on one problem - Snape didn't know that James was animagus, which means that he might not have associated Lily's patronus with him.
By the way, do students teach the Patronus spell? Harry demonstrates Patronus to OWL, this is "aerobatics", he should not know this idea at that time. But probably, they learn later? It is possible that Snape saw James's and Lily's patronus, when they were taught, in the seventh year is permissible.
Or maybe they weren't studied at school at all, and, say, Snape taught Lily to call the patronus. Finally she was so interested Dementors ...