@deactivated843b8160732
Well, we found out. There was Reborn one when Time Lords gave him mroe lifes, due to the Time War. And the War Master (Derek Jacobi) was the 17th. Simm one 18th. Missy 19th. Lumiat 20th. And the Spy one who face Jodie Whittaker’s Doctor was the 21st.

Oh, please, tell celestia her royal hindquarters doesn’t look as good,
 
_{Because I won’t do it}

Mugen: When I turned 900 years old, I had 55 years left in my third human cycle. And I had a few left before I got out of it and into the kind of life, or existence, I have now.

@Background Pony #1D01
 
So long as he’s able to get a new cycle when he hits the final incarnation of the one he’s on. That’s what saved him at Trenzalore, and would’ve helped the Master if he’d made it back to the High Council after the whole affair with Borusa and the Death Zone.
 
In fact, I think that’s how they brought him back after he’d been exterminated by the Daleks at the start of the TV Movie. I just wonder what number incarnation Jacobi was in that cycle. I mean, the Master could’ve regenerated exactly eleven times before fleeing the Time War and taking refuge as Yana. For all we know, Simm could’ve been the last.

The Doctor lies about his age.

Immortality doesn’t automatically mean invincibility. It might well be possible for Celestia to die. As for the Doctor, he can definitely die, and he’s not even technically immortal. He might have plot armour, but he at least in theory has a limited number of regenerations.

At least Yoda could die.
 
Immortality is a really shitty thing. A long life of power = gusta
 
Living forever = Toss self into a sun repeatedly, eventually lose mind