Originally Posted by Virgil Tracy:
“I think everyone was just expecting her to leave including herself and Moffat , but then they probably asked themslves "well why ? why not stay instead?"
.”
Yes, maybe she didn't want to leave at all but felt she
had to because had she gone at the end of Last Christmas, that would have been 25 episodes. Compare with Billie Piper who left after 27 episodes (but then returned for several guest appearances and cameos). Maybe Jenna felt she'd had her fair share.
As a rule, it might be said, the companions should have shorter runs than the Doctors and the standard for the Doctors seems to be 3 series and a few specials. When Jenna goes at the end of the next series (assuming!) she'll have had two and a half series. In fact, more than because her half of series 7 was considerably more than Karen and Arthur's. They had 5 episodes; Jenna had 8 episodes plus 1 of their five plus the Christmas special in between.