window of opportunity

window of opportunity (plural windows of opportunity)

1. A period of time in which suitable action can achieve success.
   • 2013, Martina Hyde, Is the pope Catholic? (in The Guardian, 20 September 2013)

     The Lord moves in mysterious ways – though not a thousandth as mysterious as those of his senior personnel from time to time – so there is no earthly possibility of predicting how long the window of opportunity enjoyed by Pope Francis is likely to be.