Chaosmagnet has a good point. If you are going to leave the time to do it before everyone else clues in. In that respect, there is some aspect of wisdom in the suggestion that it is always safer to leave, but the reality is this only works if you decide to leave ahead of everyone else. And even that wouldn't work if everyone took the same strategy.

So if you do plan to bug out as a default the trick would be to do it at the first hint of trouble, rather than waiting for definitive signs.

-john