I really like what Open Eyes said--these are the-limited events.

The adrenaline response (fight/flight) that gets triggered by a flashback has about a 20 minute life span. When I get triggered into a flashback now, I often try to check my watch-- and sure enough, after about a half hour I am less panicky and exhaustion or numbness have set in. When it is happening, it feels never ending. But the body reacts to triggers in predictable ways, and knowing this can make it seems less timeless and interminable.