Incorrect-Some leave them, some take then down. NITE and two to three others take their orders off and stop providing quote/liquidity, while others leave them up, all dependent on the respective MMs and what they choose to display/execute. If they can match a buyer and seller, upon them as to when they want to execute....seen after hours all the time and pre-market all the time, even in OTC land...there is no definative answer here...while MOST trades occur during market, often times action occurs pre/post, and usually with news...
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