A/N: I know a lot of people don't like songfics, and I know the Dean-dies-and-Sammy-goes-insane-fics have been done to a crisp, but whatever. This popped into my head, so I had to type it.
I also know that it's never explicitly stated what day or time the deal happens, so I decided on Monday because that's when Supernatural is on TV here in Aus. As for the timing, I guessed late in the evening.
Disclaimer: All songs quoted or mentioned in this work of fiction are the property of their respective artists, and are only used to illustrate a point.
Supernatural is the property of Eric Kripke and the CW, as are all characters mentioned, bar my OCs (who are also only to illustrate a point).
The Wish List is the property of Eoin Colfer. Not me.

MONDAY
T-168 hours

They're driving again. They've been driving for nearly a whole day now. Sam's bored and has a headache, but he's still trying to ignore the fact that Metallica is making his head hurt even more. He doesn't want to snipe at Dean anymore - he only had a week left. One minute to midnight.
I guess it's times like these that make you appreciate things. Like how hunting made me appreciate the fact that I was alive. And now...it feels like we've just looked at the deal and gone, 'Yeah. Whatever' and gone on with our lives. It feels like we haven't even tried to do anything.
Gotta keep researching. Gotta find something.

Sam sighs, and Dean looks at him out of the corner of his eye. He knows Sam's running himself into the ground, slowly but surely. He knows that this is killing him. God, he's so skinny now! It makes me think of when he first got freakishly huge, he was like a friggin' stick figure!
Dean knows why Sam takes his clothes into the bathroom with him when he showers - he doesn't want Dean to see that he's lost so much weight, but it doesn't take Einstein to see that Sam's slowly dying from exhaustion. Not just outside, inside too.
Sam doesn't talk much anymore. When he does, it's only to refuse offers of food, entertainment, or jobs, or sometimes to return a half-hearted attempt at banter. Sometimes, though, Dean thinks he can hear Sam mutter, 'it's Sam' when Dean calls him 'Sammy', or murmur 'Jerk' when Dean calls him 'Bitch'. It sounds pretty good to Dean; to him it means that the old Sammy is still hiding somewhere. But he doesn't respond to Dean much beyond that, except to snipe at him over the deal; that doesn't hurt him anymore. Dean's beyond the arguments, the fights, every attempt to talk him around and tell him what he did was wrong. Dean died a long time ago, three hundred and fifty-eight days ago, to be exact. Dean died when a knife went through his little brother's back, severed his spinal cord and punctured his heart. Dean died when Sam died in his arms; he's just going through the motions now.
The song changes. Dean hasn't heard this one before, and he looks at Sam.
This yours?
Sam doesn't respond. Dean takes it as 'no'.

The song has a long intro, but as soon as the guitars come in, Dean knows exactly who made this. The intro continues, nearly a minute and a half, but Dean doesn't care - Metallica and long intros are synonymous. It's the lyrics that catch him. He nearly drives through a red light when he hears them.

Pay no mind to the distant thunder,
New day fills his head with wonder, boy...

Says it feels right this time,
Turned it 'round and found the right line,
"Good day to be alive, sir,
Good day to be alive," he says...

Then it comes to be, that the soothing light at the end of your tunnel,
Was just a freight train comin' your way, yeah,

Dean clenches his teeth and tries to ignore the song. He wants to just fast-forward, or eject the tape and throw it out of the window, but he can't. It's strange, but Dean just can't bring himself to stop listening.

Don't it feel right like this?
All the pieces fall to his wish,
"Sucker for that quick reward, boy,
Sucker for that quick reward," they say

That's it. Dean angrily jabs the 'eject' button on the tape player, and the tune cuts out in the middle of the chorus. The tape is thrown into the back of the car, and Dean drives on, Azazel's words and the lyrics of the song twisting themselves about in his head.
Are you sure what you brought back was one hundred percent Sammy?
"Sucker for that quick reward, boy, sucker for that quick reward."

Sam can't help but think, that was strange.

Later that night, Dean is driving again, and Sammy is asleep in the passenger's seat. They have a job, hunting down the murderer of people on a run-down property in Random Small Town Number God Only Knows What.
Damn, I'm cynical. Need some better music to cheer me up.
Dean selects another tape, and Highway to Hell greets him. Yeah. This is more like it.

Ten seconds later, another tape joins the first in the back of the car.