Clement of Alexandria (150-215 A.D.)
"So he saves all; but some he converts by penalties, others who follow him of their own will, and in accordance with the worthiness of his honor, that every knee may be bent to him of celestial, terrestrial and infernal things (Phil. 2:10), that is angels, men, and souls who before his advent migrated from this mortal life."
Source: The Stromata (also known as Miscellanies), specifically in Book VII, Chapter 2.
And
"For all things are ordered both universally and in particular by the Lord of the universe, with a view to the salvation of the universe. But needful corrections, by the goodness of the great, overseeing judge, through the attendant angels, through various prior judgments, through the final judgment, compel even those who have become more callous to repent."
Source:Book VII, Chapter 12 ofthe Stromata (also known as the Miscellanies.)
Theodore of Mopsuestia (Bishop of Mopsuestia from 392 A.D. until his death in 428 A.D.)
"The wicked who have committed evil the whole period of their lives shall be punished till they learn that, by continuing in sin, they only continue in misery. And when, by this means, they shall have been brought to fear God, and to regard Him with good will, they shall obtain the enjoyment of His grace."
Source: Bibliotheca Orientalis
Diodore of Tarsus (Bishop of Tarsus from 378 until his death in 393 A.D.)
"For the wicked there are punishments, not perpetural, however, lest the immortality prepared for them should be a disadvantage, but they are to be purified for a brief period according to the amount of malice in their works. They shall therefore suffer punishment for a short space, but immortal blessedness having no end awaits them. For the penalties to be inflicted for their many and grave sins are very far surpassed by the magnitude of the mercy to be showed to them."
Source: Bibliotheca Orientalis.
Theodoret the Blessed (Bishop of Cyrrhus in Syria from 423 to 457 A.D.)
"In the present life God is in all, for His nature is without limits, but he is not all in all. But in the coming life, when mortality is at an end and immortality granted, and sin has no longer any place, God will be all in all. For the Lord, who loves man, punishes medicinally, that He may check the course of impeity."
Source: Theodoret of Cyrus, Commentary on the Letters of St. Paul, vol. 1, trans. By Robert Charles Hill (Brookline, MA: Holy Cross Orthodox Press, 2001), 1 Cor 15:28
Note: A Comment from a 6th century non-Christian, Pagan (neo-Platonist) Philosopher would appear of relevance to how the Greek words aionian, aionios, and aionas (commonly translated eternal or everlasting) were used and understood in the Pratrasic era.
"Do not suppose that the soul is punished for endless eons (apeirou aionas) in Tartarus. Very properly, the soul is not punished to gratify the revenge of the divinity, but for the sake of healing. But we say that the soul is punished for an aionion period (aionios) calling its life and its allotted period of punishment, its aeon."
Source: Olnmpiodorus the Younger (AD 550)