Yes the time of mercy will expire with no more warning:
“Concerning that day and hour nobody knows, neither the angels of the heavens nor the Son, but only the Father. 37 For just as the days of Noah were, so the presence of the Son of man will be. 38 For as they were in those days before the Flood, eating and drinking, men marrying and women being given in marriage, until the day that Noah entered into the ark, 39 and they took no note until the Flood came and swept them all away, so the presence of the Son of man will be. 40 Then two men will be in the field; one will be taken along and the other abandoned. 41 Two women will be grinding at the hand mill; one will be taken along and the other abandoned. 42 Keep on the watch, therefore, because you do not know on what day your Lord is coming.
43 “But know one thing: If the householder had known in what watch the thief was coming, he would have kept awake and not allowed his house to be broken into. 44 On this account, you too prove yourselves ready, because the Son of man is coming at an hour that you do not think to be it.