The "close of probation", as it is sometimes called, is the point in time when every person on Earth will have chosen for the last time, who they will trust. The time before this "close" is a "Probationary" time, but as its name implies it will not last forever.
As noted above, the Bible says that there will come a time when those who are "good" will remain "good" and those who are "bad" will remain "bad". It is also clear that the point in time when this happens is sometime before Jesus comes; note the first part of Revelation 22:12, "And, behold, I come quickly...".
God will place "the seal of the living God" on His people (Revelation 7:2, 3) and those who have not chosen to trust God will receive the seal of the Beast (also known as the Mark of the Beast as noted in Revelation 13:15-18).
The period of time between the "close of probation" and Jesus coming will be very short. There will be no need to wait because all are sealed, and so whatever time it takes for Jesus and all the angels to leave Heaven and arrive at Earth is all the longer this period of time will most likely be.