The Doctor always seems to have his "main" companion at any given time. Right now it's Clara. Some of the Doctor's companions have been given permanent endings. Amy and Rory got trapped in the 30s. Donna can't remember the Doctor without her head exploding. Rose is sealed off in another dimension. But then we have characters like Martha and Jack Harkness. Martha chose to leave the Doctor at the end of her season, but she was still alive and well. She started working for UNIT and popped up a couple times in Season 4. It got me thinking; I'd like to see more of this, and I'd like it to start with Clara. Even if Capaldi's Doctor has a new fulltime companion once Clara leaves, I'd like her story to allow for the possibility of her return. She already doesn't live on the TARDIS like other companions. The Doctor has adventures with her and drops her off at home. She has a life and a job away from him. I guess I'd just like more open-endedness with some of the companions. I'm getting a little tired of these permanent, tragic finales where the Doctor can never, ever see his friends again.
I agree. I know this is a particularly special case, but it was always a treat to see Sarah Jane Smith meet up with the more recent Doctors. And K9, too! I wouldn't mind seeing Jack or Martha again. Or Ace!
I'd say that Clara is already a recurring companion. She doesn't live in the TARDIS and travel with the Doctor continuously; she lives at home and leads her normal life, and the Doctor occasionally drops by to whisk her off on an adventure and get her back in time for tea. She's not even a proper companion, since she hasn't committed to the life. She's just a friend. Indeed, Amy and Rory were the same way in their later tenure -- moving on with their life, with the Doctor occasionally dropping by to whisk them away from sanity for a while. Which made it all the more ridiculous that they had to be "killed off" altogether in some big dramatic ending, instead of just drifting away from the Doctor and mutually deciding they should move on with their own lives. I always regretted that the classic show so rarely brought back old companions. The only times it ever really did were in "The Five Doctors" and "The Two Doctors." The Brigadier came back a couple more times, but he was never technically a companion. Harry Sullivan came back in "The Android Invasion" (along with Benton), but that was only two months after his tenure as a companion ended. Other than that, it pretty much never happened. Well, they did try to give Sarah Jane and K9 a spinoff, but it didn't get off the ground.
I mean more in terms of episode appearances. Clara is still a fulltime companion [to us] because she's in every single episode. Same with Amy and Rory. But when she leaves and we've moved on to another companion, I'd like for Clara (or whoever) to still be able to pop up once or twice, much in the way that Martha did. I think it would also be fitting for Clara as the girl whose story began as a tragedy. We met her in the Asylum; she died. We met her in Victorian London; she died. How great would it be if this one time she was the companion who lived happily ever after? No alternate dimensions. No mind-wipes. Just a normal girl with a normal life who occasionally gets to see her friend the Doctor when he pops into town.