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ost_uid0]According to the episode guide at Outpost Gallifrey, there were 712 25-minute episodes (or equivalent) over 159 serials between Nov 63 and Dec 89. Yeah, that's a lot of fiving.
What's interesting is that the early Doctors worked a lot harder. Season One had 42 episodes over 8 serials. They actually had to write the Doctor out of individual episodes ("Look! The Doctor's collapsed!" or "Where'd the Doctor go?") just so he could have a measly week's holiday. Imagine a whole episode without Kirk. (Mmmmm, pleasant.)
Season 26, by contrast, had 14 episodes over 12 serials. Sylvester McCoy barely had to work at all.[/color

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