A *Doctor Who* question

Hello, there! I'm currently stirring up my brain to concoct an essay for A teaspoon and an open mind, but I have a wee question, thus:

I have a distinct impression that, of the people of Gallifrey, only the Time Lords (the ruling elite) can regenerate, while the "ordinary citizens" -- the farmers, cobblers, plumbers, et alia -- live only one life, like us humans.

I'm not sure where that impression comes from though. Is there evidence in any of the aired episodes themselves, or is this just a fandom favorite idea?

Yours, in curiousity -- Me.