Here is St John Chrysostom's Homily V on the gospel of Matthew 1:25, commenting on εως ου:
"And when he had taken her, he knew her not, till she had brought forth her first-born Son.' He hath here used the word till,' not that thou shouldest suspect that afterwards he did know her, but to inform thee that before the birth the Virgin was wholly untouched by man. But why then, it may be said, hath he used the word, till'? Because it is usual in Scripture often to do this, and to use this expression without reference to limited times. For so with respect to the ark likewise, it is said, The raven returned not till the earth was dried up.' And yet it did not return even after that time. And when discoursing also of God, the Scripture saith, From age until age Thou art,' not as fixing limits in this case. And again when it is preaching the Gospel beforehand, and saying, In his days shall righteousness flourish, and abundance of peace, till the moon be taken away,' it doth not set a limit to this fair part of creation. So then here likewise, it uses the word "till," to make certain what was before the birth, but as to what follows, it leaves thee to make the inference. Thus, what it was necessary for thee to learn of Him, this He Himself hath said; that the Virgin was untouched by man until the birth; but that which both was seen to be a consequence of the former statement, and was acknowledged, this in its turn he leaves for thee to perceive; namely, that not even after this, she having so become a mother, and having been counted worthy of a new sort of travail, and a child-bearing so strange, could that righteous man ever have endured to know her. For if he had known her, and had kept her in the place of a wife, how is it that our Lord commits her, as unprotected, and having no one, to His disciple, and commands him to take her to his own home? How then, one may say, are James and the others called His brethren? In the same kind of way as Joseph himself was supposed to be husband of Mary. For many were the veils provided, that the birth, being such as it was, might be for a time screened. Wherefore even John so called them, saying, For neither did His brethren believe in Him.' "--John Chrysostom, Gospel of Matthew,V:5 (A.D. 370),in NPNF1,X:33 for Greek text go hereLet's look at the proof texts St John Chrysostom uses:
The raven returned not till the earth was dried up.'--Genesis 8:7His usage of this verse seems to be a paraphrase, or based on a version of the LXX that I do not have access to. This quotation does use εως ου, the LXX version I have only have εως, in any case how St John uses it in a sentence shows its possible to use.
This other text is Psalm 89:2 in the LXX (which is Psalm 90:2 elsewhere), it reads:
From age until [ἕως] age Thou art--Psalm 89:2 LXX
ἀπὸ τοῦ αἰῶνος ἕως τοῦ αἰῶνος σὺ εἶ--Psalm 89:2 LXXUnlike, the first text from Genesis 8:7, this one is an exact quote. The Psalm does not use ἕως ου, but simply ἕως, showing St John felt demonstrating ἕως by itself was sufficient to show the meaning.
His third text is:
In his days shall righteousness flourish, and abundance of peace, till [ἕως οὗ] the moon be taken away—Psalm 71:7 LXX (Psalm 72 in the most bibles)This text is also a verbatim quote of the Septuagint. However, unlike the last two quotes, this one does contains the phrase ἕως οὗ. Obviously, the Psalmist did not intend to say that righteous and peace will cease once the moons goes away!
ἀνατελεῖ ἐν ταῖς ἡμέραις αὐτοῦ δικαιοσύνη καὶ πλῆθος εἰρήνης ἕως οὗ ἀνταναιρεθῇ ἡ σελήνη --Psalm 71:7 LXX