All good things come to an end eventually but fans of The Walking Dead have nothing to worry about for now. The zombie apocalypse has just premiered season six and one of the show's directors, Greg Nicotero, has promised it will remain on screens for many years to come.

Since 2010, viewers have watched as group leader Rick Grimes, played by Andrew Lincoln, has fought to survive in the apocalyptic world while protecting his children, Carl and Judith. The former police officer has made – and lost – a slew of new friends along the way, including Daryl, Carol, Michonne and Glenn, the last of whom met his fate in the most recent episode, Thank You.

It has certainly been an emotional journey so far and Nicotero says it is far from over. The director told the IBTimes UK at a press launch in London: "I think we have several more years ahead of us. I think [series creator Robert] Kirkman said 11 or 12. It's just about introducing those new characters, getting Enid, Spencer and Aaron in there.

"You want to keep the ensemble growing and keep those characters interesting but it is unimaginable that we're six seasons in and we still have people watching the show. Our ratings in the States dropped a little bit and everyone's like that's the end of Walking Dead! I'm like, you guys suck it because I've never heard of a show that still gets almost 20m viewers and people think [we] should just hang it up and go home."

Watch The Walking Dead season six episode four trailer:

With the survivors now taking up residency at safe zone Alexandria, Rick's group has only increased in size and Nicotero promises viewers will get to know some of the new faces over time. The special effects supervisor explained: "The world of the characters grows and if anything, Scott M. Gimple wants to make sure that those additional characters aren't just glorified extras.

"We spend a lot of time casting these people and I cast Katelyn [Nacon] who plays Enid because she was in the first episode I directed when they were in Alexandria. Even with Lizzie and Mika in previous seasons, we spend a lot of time casting these people and it's tricky because if they don't have much to do they just look like they are window-dressing. We want to expand our world and by giving insight into other characters' backgrounds, it makes it richer. Not every character is successful, people say: 'I don't like that, when are you going to kill Father Gabriel or Tara'. But there are stories there for them and you need that balance in the show."

The Walking Dead airs on Mondays 9pm on FOX in the UK.