Dean knew that they would never make it out alive. Because Winchesters never do. But that's okay.
Dean was the first to die, when Sam eventually said yes to Lucifer, again, in 2014, and he used Dean's brother to snap his neck. But that's okay.
Sammy was strong enough to annoy Lucifer from time to time, but never strong enough to take back his body, but he was never really gone. So when Michael and his army fought to take down Lucifer, and it just so happens that Castiel was the one to end his fallen brother once and for all, Lucifer died before Sam did, and Sam died in the comforting embrace of someone he called family. But that's okay.
And after the threat of Lucifer was taken care of, there was a mad scramble for power, in which Michael quickly eliminated his competition, including the threat of Castiel, The Angel of Thursday. But that's okay.
Because they may have known that they were never going to live a long happy life, but the Winchester brothers also knew that they'd always be together, and they were. In their own heavens, there had many places in common. They went to the bunker together often, where they saw Kevin and Mama Tran. Kevin liked it because he felt safe there and Mrs. Tran liked the space, and the smile on Kevin's face when he saw Sam and Dean again. Another location that they had in common was Bobby's house, where they visited him and Karen often. The Roadhouse was also a place they popped in on whenever they got a chance. While sitting around the bar with Ash, Jo, Ellen, and Pamela, they started to accept their new lives which were, admittedly, much less exciting, but more fulfilling than their previous ones. They went and saw their mother from time to time, at their house in Lawrence, but it was hard because of all the bad memories they had, while she had only the ones of her and John fighting. They never did see their father, and that was alright with all parties involved.
Along with their family, they also shared spots that were just theirs. They had a rock concert that they had snuck into when Sam was 14. They had many nights spent sitting on or around the Impala drinking beer, stargazing, each lost in their own thoughts, but glad to have their brother with them.
Of course they had their own separate heavens as well. Sam had a normal life with Jess and their new baby girl, Amelia, like he had always wanted, but knew he would never have in life. They didn't have to work, so most of their time was dedicated to tending to and loving Amelia. The small suburban neighborhood that their "home" consisted of was not perfect. It was a small place with few problems, such as bad plumbing in old houses that Sam helped fix. Jess helped struggling parents mend clothes, and budget their expenses. Of course none of this was needed, and should they wish it away, it would go away, but Sam and Jess Winchester need people to take care of.
Dean's perfect life was different. He spent several months after his death alone. It wasn't much of a Heaven at all. Sure he could see Sam, but it was an echo of him in Dean's memories, it wasn't his Sammy. He missed Castiel too. Of course he did. But he also knew that angels couldn't come back to Heaven after Metatron closed it. So there was no more Cas. There were the echoes of him that Dean clung to whenever he saw him in a memory of the bunker, or when he told Cas to blow him at Bobby's place, and Cas looked so confused. Dean loved him then. He had loved him ever since then. But he knew that like Sam, he couldn't be happy with the person he loved in life. He was hoping that when he made it to heaven Cas would be there with him, but it was not to be. He kinda figured after all the bullshit Sammy and he had gone through for God's mistakes that they'd get a ticket upstairs when it was really their time to go. He wasn't wrong.
Then one day he saw Sam. And Sammy saw him. Really saw him, and ran up and bear hugged his shorter, older brother. And they both shed tears that they tried in vain to hide. Sam was crying because he was there when Lucifer snapped his brother's neck, and that was the last he saw of him. Dean cried because Sammy was here. He was dead too. Dean did everything he could to keep him alive, and he failed. After a few weeks of hating himself as much as he had on Earth, he opened up to his brother, who told him to shut his stupid face, and listen, because he was glad that he was here, it meant they were free. Their job was done. No matter what happened now, they couldn't stop it, and it wasn't their job to. But that's okay.
For a little while, or maybe an eternity, its hard to tell in Heaven, Dean was happy. He was free to do whatever he wanted; he could work on his Baby all day, or just listen to music. If he wanted to he could spend all day with Bobby, or his mom, jeez he had missed her.
But he got lonely. And bored. Sam had his family, and he was happy for his brother's happiness, he really was, but he had hoped Heaven would be more, well, Heavenly. He ignored his missing Cas, but every time he saw one of those shadows of the man/angel/celestial being/person he loved, it hurt worse and worse than going this long without having a clue whether he was dead or alive. What even happened to angels when they really died? They didn't go to purgatory because Cas was the only one those monsters had seen in forever. They didn't go to Hell because angels and demons didn't mix. Did they go back to Heaven? If they did before, did Metatron make it so they couldn't before Cas stopped him? Sam had told Dean what he had gathered from being Lucifer's angel condom; Cas' grace did have something to do with knocking Metatron out, and when he did kill Metatron, he got his grace back. Sort of. He could heal himself, and minor injuries on others, but he couldn't bring people back, or fly, and he could only tune into angel radio if someone wanted him to. He was an angel still, but not. But that's okay.
Maybe that's why when Michael stabbed him in the chest, his eyes didn't light up with his grace. They darkened with the life leaving his body as it was his, Jimmy was long gone by that point. Maybe that's why one day Dean woke up to him in his room in the bunker. And when Dean looked over and saw Castiel, The Angel of Thursday, asleep next to him, he knew this was not from memory, and he knew that Cas was here with him in Heaven finally. He didn't care how or why, all he cared about was that Cas' idea of Heaven was being by Dean's side, so when he woke Cas up with a kiss, it didn't take him long to return the gesture.
The Winchesters knew they wouldn't live a long life. But that's okay.
A/N: Dude I have had this floating around in my head for a few days and I needed to get it out, shoutout to my gloriously wonderful beta, destieljohnlockinthetardis, link to her page here- u/5179026/ , for putting up with my not updating my other story for weeks, and then throwing another one at her at 10:30 at night to beta because I don't want to wait until morning. Thanks to anyone who reads this, hugs to all who follow/favorite/review SHITTY WRITER OUT