Not long. The Israeli move was prompted by Nasser sending most of the Egyptian army into Sinai, including troops who had just returned from the Yemen Civil War, where Egyptian forces had used mustard gas on Yemeni villages. On the eve of the war the Egyptian army had all seven of its divisions in the Sinai. The Syrian and Jordanian armies were also concentrated in forward positions. Nasser was also increasing the political pressure and public rhetoric in preparation for war.
When the war did break out on June 5th, it was not a strategic surprise to the Arabs; the entire Egyptian air force had scrambled at dawn, ready to meet any Israeli attack in full force. However, anticipating this, the Israeli’s didn’t attack at dawn, attacking an hour later, catching the Egyptians on the ground and refuelling.