Season five is set in the autumn of 1987. Hawkins, Indiana, is scarred by the opening of the Rifts and the group of friends must find and kill Vecna. At the same time, the town is under military quarantine as the hunt for Eleven intensifies.
The brothers, who were in their early thirties when the show began, had always planned for four or five seasons, but say it still feels surreal that they managed to get that far.
There have been reports that not everything has been plain sailing. The Mail on Sunday recently reported that Millie Bobby Brown filed a harassment and bullying claim against her co-star David Harbour, but that hasn't been confirmed.
However, the cast insist there's a close friendship between everyone, while the Duffer brothers say they felt an immense responsibility to protect the younger cast throughout filming.
"When we cast them we didn't know the show was going to be what it was and you hear so many horror stories about young people that become famous as the spotlight can be harsh," Ross says.
"I think it helped that there were so many younger cast members so they weren't going through anything alone and could turn to each other during challenging times."
That solidarity was a vital help for Finn Wolfhard, who plays Mike Wheeler and says growing up in the spotlight was a challenge "because you're going through puberty and a life change like being part of Stranger Things at the same time".
His on-screen, and perhaps also off-screen, best friends Caleb McLaughlin and Gaten Matarazzo agree, and the trio start laughing about how young they were when they first met.
I ask the young men how they feel about the show ending and stepping into new projects, and Gaten is first to admit they feel some trepidation.
"I'm a bit shaky and there is a bit of anxiety, but I think that's the point."
The 23-year-old, who plays Dustin Henderson, says now feels like a good time to step into a period of unknown.
"Your twenties are all about change, transition and growing, and we're incredibly lucky to be in a position to establish consistency in our careers.
"I see that as a real blessing and I look at it optimistically as I can because it is scary to not have the comfort of knowing there's another Stranger Things season."
The legacy of the show is undeniable - it's transformed a cast of newcomers into stars and spawned a global fanbase who have grown up alongside it.
Caleb hopes that connection lasts and the show "lives on and becomes one of those things that people will rewatch and never get tired of, like a classic film".
Knowing the impact of the show made saying goodbye even harder, and the final day of shooting is something Caleb won't forget for a while.
"Everyone was there and it bought us back to episode one - that feeling of home, being supported and loved, and everyone was on the same page in terms of their connection with the show," he says.
Netflix has announced an animated follow-up, while details of the Duffer brothers' live-action spin-off are still under wraps.
It's the end of an era for the current cast. But would they reunite for another project?
"Our part of the Stranger Things story is done for now," Gaten says. "But if they called us in a while, who knows?"
The first four episodes of season five will be available in the US from 26 November, with the next three arriving on Christmas Day, and the finale on New Year's Eve. In the UK those releases will be a day later.