The council did not close with the Greek union. Separate bulls extended the same formula to the Armenian Church in November 1439 and, after the assembly moved on to Rome, to the Coptic and Ethiopian churches in 1442 and to Syrian, Chaldean and Cypriot Maronite communities through 1445, so that the council's full span is usually given as 1431 to 1445 across its three phases.
None of the unions proved durable. The Florence agreement was repudiated by most of the Byzantine clergy and populace once the delegation returned home, resented as a concession bought under military necessity rather than a settled reunion, and it collapsed entirely after the Ottoman conquest of Constantinople in 1453 ended the empire that had sought it. Meanwhile the rump that remained at Basel after Eugene IV's transfer refused to disperse, declared the pope deposed, and elected its own antipope, Amadeus of Savoy, who took the name Felix V, prolonging the conciliarist crisis into the 1440s until his eventual submission. The Greek scholars who traveled to Florence for the council, Bessarion foremost among them, remained an enduring legacy of a different kind, carrying Greek manuscripts and teaching into Italy at the same moment the city's own revival of classical learning was gathering pace.
Bessarion remained in the West after the council closed, was made a Latin cardinal within the year, and spent the following decades assembling one of the era's great libraries of Greek manuscripts, later bequeathed to the Republic of Venice, a legacy that outlasted the union he had signed for by centuries.