Unfortunantly, at this time, the rules regarding a direct question apply only to the Against the Mainstream section. Although we have discussed expanding that (and a few other ATM rules) to this section, to date we have not reached concensus. So, for now, the answer is: as long as they want.
(psst--don't tell anyone! )

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All civilizations become either spacefaring or extinct.~ Carl Sagan ~

Humanity must rise above the Earth, to the top of the atmosphere and beyond, for only then will we fully understand the world in which we live.~Socrates, 500 B.C. ~

Let every man judge according to his own standards, by what he has himself read, not by what others tell him. ~Albert Einstein~