It has been said that we don’t talk enough about Sam and Dean’s codependency (or enmeshment, ymmv). Sad, but true😔. So, let’s talk about Sam-Dean and sacrificing some more.
In 2x22, Dean did initially try for more years of togetherness but ultimately had to settle with only one year. At this point, as those that had watched s1 would know, Dean didn’t believe in heaven/god/angels. So, Dean’s deal here was about togetherness.
In 4x09, Sam is shown at an all-time low. Drunk, mourning and probably still thinks he deserves death for being a monster/other instead of life/good, doubly so if it means the cost of his brother-wife. So, he calls up a crossroads demon to demand/barter/exchange himself for Dean. In this instance, the goal is not them being together. Honestly, we all know that is the preferred option given how they’ve interacted with each other the full run of the show. (Personal space, doors, and separation are the real big bad.) But, Sam will give that up if it means his bro-for-life is safe. Safe, not necessarily happy.
This leads us to 5x22. Sam’s sacrifice for the world and ultimately his brother. The episode for all those people asking where was Sam’s happy memories of his brother in heaven if he loved Dean so much. And they were right there in that flashback. Memories so powerful/good/loving/happy/together-ful that Sam overtook the devil and dragged both archangels in the cage, along with Adam 💀. Anyways, Sam yet again gave up being together for his brother to be safe. He already knew from experience his brother would be upset. But, He hoped Dean could find a way to move on and be at peace with Lisa. (Though, 6x01′s domestic mourning montage and Dean telling soulless that he rather his brother be alive tells us that was not the case. Poor Lisa and Ben. Glad, they didn’t hear that.💀)
In 8x23, Sam was about to make a new sacrifice for the world/his brother, locking all the demons up in hell via the trials. And when he found out he was going to die he still didn’t want to stop. But, Dean gave him his own puppy eyes and said something like, “No, Sammy, babe. 🥺We/Us. Sam!exception. Together!chesters.” And Sam was like, “😐... You’re so totally right. Bros-forever.💕” Then they get bro-married and hug it out. So, they decided they’re safer together and that’s what matters. They’ll get all the demons locked in hell later. The world’s safety was pretty much sacrificed here.
In 10x23, another sacrifice was set up. But it started out the opposite of the other times. Dean wasn’t going to sacrifice himself this time, but Sam and their togetherness for the safety of the world. Except Sam gave MoC!Dean puppy eyes and family pictures and told Dean how good he was, and Dean was like, “I’m so sorry I have such good taste that the world has to suffer, Sammy 😐,” and stabs Death. So, the bros stay together and the world gets the Darkness.
Then 11x17 happens next season. Dean decides to sacrifice himself thinking Sam kicked the bucket due to his injuries and not the incognito werewolf victim choking his brother-partner behind his back. He wanted Sammy to be alive rather than them being together. Probably doubly fueled by one of Dean’s greatest fear that was established again in the episode before, Sam dead but Dean still alive (📣11x16, #Soulmates). And, probably Dean being down about being connected to the Darkness a little too.
After that I believe was the 13x23 sacrifice. Dean took on Micheal to save Sam, and Jack too, from Lucifer. No one supposedly was going to die from this deal if everybody kept their word. So, this sacrifice was so Sam and Dean could technically still be together in the end and also technically for the world to be safer with Lucifer dead. But, optimism aside, if all else failed Sam (and Jack) were safe from Lucifer at least.
In the next sacrifice, 15x17 Dean was going to sacrifice Jack for both Sam and Dean. (Rip to the Dean&Jack relationship tag in 15x17 though. Ouch.💀) But then, Sam stopped him with puppy dog eyes and referenced Dean’s Sam!exception. Sam wasn’t against together!chesters because he was like we’ll figure it out together. But, Sam was sus of Billie, with good reason, and didn’t think sacrificing Jack was worth whatever they got as consequence, good or bad.
In 15x19, Dean brings up sacrificing Sam&Dean’s life for humanity, birds, and Cas. It doesn’t technically go against together!chesters, because they would be going out together. No telling what Chuck would do with them afterward, but, Chuck didn’t want the Cain and Abel thing anymore, so we’ll never know.
And lastly, 15x20, the last sacrifice, which I like to think of as Sam not bringing back Dean for together!chesters, because it was Dean’s wish to not do so and because it always messes up the balance of the world. And, I like to see it as both Sam and Dean knowing they’ll be together for all eternity in the end anyways. What’s (however long Sam’s montage was) more years? So, like it’s against short term together!chesters but it is thinking for long term together!chesters.
So, yeah, together!chesters isn’t always the main-main theme each and every time, but it is a big part of it and a very close contender for the other brother being “safe”.