When Does A Phrase Become A Cliche?

To become a cliche or stale, a phrase must once have been fresh. "To avoid something like the plague" must have been a very vivid and meaningful simile around the time of the Black Death, but in a country where the plague hasn't been a threat for over 300 years, it has lost its force.
George Orwell gave the best explanation of how cliches evolve in his essay "Politics and the English Language." He said that the problem was with writers using phrases without thinking about what they actually meant (e.g "hammer and anvil", without knowing that the anvil can break the hammer, but not vice versa.)
A contemporary example of this is the phrase "rein in" meaning, literally, to control (as in pulling the reins to stop a horse.) This is often misspelt ("He'll have to reign in his spending") by journalists who don't know what the original metaphor meant.
Put simply: cliche is language used without thought, or without any real wish to communicate.

I think cliches are like vocabulary that is passed down in families.  Many cliches that we Americans interchange with words to get a point across have European roots.  Don't let the cat out of the bag=French.  Don't throw the baby out with the bath water=Irish and so on.  I wonder if the huge population of citizens with Asian or Hispanic origins have a clue as to what these cliches mean.