Once God ends the dispensation of His grace, the current offer will be done and finished. That time is at the catching away.
God's dispensation have a beginning and an end. That is why God declares a different gospel during the tribulation:
Rev 14:6-7 (AKJV/PCE)
(14:6) And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people, (14:7) Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and worship him that made heaven, and earth, and the sea, and the fountains of waters.
Remember that Paul warns us NOT to listen to an angel with another gospel.
[also note that WE will not be dwelling on the earth, as our place is in heaven, Phil 3:20].
Gal 1:8 (AKJV/PCE)
(1:8) But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
Many gospels... those that believe otherwise are extremely confused.