The excessively-long author's note is available at my LJ if you want to read about the inspiration and logic behind this story (zuben-eschamali dot livejournal dot com / 70049 dot html). Otherwise, here's the epilogue:

A Land Where We'll Never Grow Old

There's a railroad trestle curving through a field of waving golden grasses, a rutted gravel track running alongside. There's a black classic car resting at a wide spot in the track, gleaming dark metal in the warmth of the midday sun. There's a tall figure leaning against the hood, legs crossed at the ankles. He's wearing ragged blue jeans and well-worn boots, plus two flannel shirts buttoned over a grey t-shirt, and he's sweating a little in the sun's warmth. He's looking out into the distance like he's waiting for someone.

Time passes.

There's the faint crunch of gravel, like a vehicle coming down the road, but it's coming from behind him. He turns in surprise to see a man in equally-battered jeans and a cracked, well-worn leather jacket climbing out of the driver's seat of what looks like the same car he's been leaning against, a smile on his face to rival the sun overhead.

"Dean," Sam says, standing up and striding towards his brother, his feet kicking up puffs of dust, a wide grin stretching his cheeks.

"Heya, Sammy," comes the warm reply, and then they're embracing, arms tight around each other, holding each other like it's been decades since they were last together.

Maybe it has been.

"Been waiting long?" Dean asks in Sam's ear, fisting his hands in the back of his shirt like he already knows the answer and doesn't want to hear it.

"You tell me," Sam says, closing his eyes and letting the sense of rightness that he's been waiting for all this time soak its way into his bones with the warmth of Dean's presence. There's sudden, fierce joy welling up inside of him, along with the peace of a promise coming true. Not that he didn't believe it would happen someday, given who'd been making the promise, but it's so damn good to be here like this, he can't even believe it.

Dean pats his back before releasing him, but he barely takes a step back. "What happened, Sam?" he asks, his voice raspy. "Why did you—" He makes an open gesture that's somehow supposed to convey the entirety of what Sam did.

Sam drops his head, remembering fire and death and horror and the way the coppery tang of blood was always in his mouth every time Lucifer allowed him to surface and see what he'd become. He hasn't thought about it for a while, but he knew that when Dean finally arrived, he'd have to at least briefly dredge up the memories. "He had the Croatoan virus," he explains. "He had a damn stockpile of it, and he was going to have his demons release it in one city every day, all around the world, until I said yes." He lifts his head, and the memory is enough to make his gaze bleak and sorrowful, even here in this peaceful place. "He said I could watch people tear apart their friends and their families, one by one, or I could let him in and be done with it. He said he'd be merciful in comparison."

"Aw, Sam." Dean's eyes hold too much pain, considering where they are. "If the damn angels hadn't yanked me away like that…"

"It doesn't matter," Sam says with a sad smile. He's had plenty of time to think, to consider the might-have-beens and the what-ifs, and he doesn't see how it could have gone any differently. Not with the hosts of Heaven and Hell arrayed against them, not with their destinies apparently written before they were born. So many possible branching points, and yet it's hard to see how they wouldn't have ended up in Detroit no matter what. "It's over, right? It's all over?"

Dean runs a hand over his jaw. "Yeah, it is. I mean, North America's pretty much a crater, but you knew that, right?"

Sam nods. He'd only caught pieces of the final battle, but after Michael had struck the fatal blow, there'd been a moment of lucidity for both of them, when Dean was freed to mourn his dying brother and Sam slipped Lucifer's tether long enough to take in the shattered world around him and give Dean a look of farewell. "I've kinda been keeping track. You know."

Dean looks around. "Don't see any clouds to peer down from." He reaches up and ruffles Sam's hair. "And dude, where's your halo? I can see why they wouldn't want to give you a harp, but what about the halo and the wings?"

Sam rolls his eyes, the reaction so familiar that his heart sings and he can't hold back a grin. "It's not like that, Dean."

Dean cocks his head to the side. "Then what's it like?" he asks, and there's a note of wariness underneath the brotherly teasing that warns Sam that there's the possibility that things up here might take a bit of getting used to.

"It's home," Sam shrugs. He reaches out and puts one hand on the Impala, who's been here with him the whole time, even if she's also how Dean arrived a moment ago. "It's—I can't explain it other than that. It's like being home." He looks at Dean, reconsidering. "Or I guess now it's like being home."

"Oh my God, you are such a sap," Dean says, but the corners of his mouth are turning up. Then he freezes. "Can I say stuff like that here?"

Sam barks out a laugh. "Say whatever you want, man."

Dean does, letting out a string of profanity and blasphemy that makes Sam's eyebrows go up. He's never heard some of those expressions, and this is the last place he would ever expect to have his vocabulary expanded like this. After a few more choice phrases, Dean finishes and looks around like he's waiting for lightning to come arcing down out of the clear blue sky. When nothing happens, he beams at Sam. "Awesome."

Sam laughs out loud, throwing his head back, and he honestly can't remember the last time he's laughed so freely and joyfully. When he looks back at Dean, the corners of his brother's eyes are crinkled with his smile, and Sam blurts out, "I'm so glad you're here, Dean." Then he ducks his head and adds, "I'm so glad I'm here." It had taken a long time to get used to the idea that he was at all worthy of it, and only a personal visit from the ultimate Judge had convinced him that he was in the right place.

"Turns out demons aren't the only ones you can make a deal with," Dean says dryly. When Sam lifts an eyebrow, he goes on, "I told Michael this was where you and I were ending up, or I was going to make so much goddamn racket in this head that he wouldn't be able to hear himself think, much less wield a sword."

Sam blinks at him. "You said that?" Who is he kidding? Of course Dean talked smack to an archangel to keep his little brother safe.

Dean shrugs one shoulder. "He said it was already foreordained, so it wasn't that big a deal."

"Huh." Sam files that one away to think about later. There are so many more important things to do now that Dean is here, so many people and places to see. And all of it comes without the responsibility and the guilt and the fear that hung over them for all of their lives and maybe even into their deaths, at least for a little while. Now, there's a whole world for them to explore.

He holds out the keys. "You want to drive?"

"You have to ask?" Dean retorts, snatching the keys from his hand. "I hope you didn't mess with my baby's radio again, or I'm gonna kick your ass."

Sam grins and pulls open the passenger side door, the familiar creak striking a comforting chord deep within him. Dean's sideways smirk across the roof of the Impala settles over him like the most comfortable clothing he's ever worn, and there's nothing in Sam's heart but peace and joy.

Yeah, this is definitely like being home.