Preaching a new gospel would require Christ to come a second time; and that’s impossible before the end

There is, however, a certain man named Nigidius, and Hermogenes, and several others, who still pursue the course of perverting the ways of the Lord. Let them show me by what authority they come!  If it be some other God they preach, how comes it that they employ the things and the writings and the names of that God against whom they preach? If it be the same God, why treat Him in some other way? Let them prove themselves to be new apostles! Let them maintain that Christ has come down a second time, taught in person a second time, has been twice crucified, twice dead, twice raised! For thus has the apostle described (the order of events in the life of Christ); for thus, too, is He accustomed to make His apostles—to give them, (that is), power besides of working the same miracles which He worked Himself.

Tertullian
Against Marcion
The Prescription Against Heretics
Chapter XXX

The Last Judgment and Resurrection of the Dead

When, therefore, the boundary and limit, that millennial interspace, has been passed, when even the outward fashion of the world itself—which has been spread like a veil over the eternal economy, equally a thing of time—passes away, then the whole human race shall be raised again, to have its dues meted out according as it has merited in the period of good or evil, and thereafter to have these paid out through the immeasurable ages of eternity. Therefore after this there is neither death nor repeated resurrections, but we shall be the same that we are now, and still unchanged—the servants of God, ever with God, clothed upon with the proper substance of eternity; but the profane, and all who are not true worshippers of God, in like manner shall be consigned to the punishment of everlasting fire—that fire which, from its very nature indeed, directly ministers to their incorruptibility.

Tertullian
Apology
Chapter XLVIII

Christ will raise and judge the same body that died

Mock as you like, but get the demons if you can to join you in your mocking; let them deny that Christ is coming to judge every human soul which has existed from the world’s beginning, clothing it again with the body it laid aside at death;

Tertullian
Apology
Chapter XXIII

Jesus second coming will be all the majesty of Deity unveiled

The Jews, too, were well aware that Christ was coming, as those to whom the prophets spake. Nay, even now His advent is expected by them; nor is there any other contention between them and us, than that they believe the advent has not yet occurred. For two comings of Christ having been revealed to us:  a first, which has been fulfilled in the lowliness of a human lot; a second, which impends over the world, now near its close, in all the majesty of Deity unveiled; and, by misunderstanding the first, they have concluded that the second—which, as matter of more manifest prediction, they set their hopes on—is the only one.

Tertullian
Apology
Chapter XXI

A thousand years in Jerusalem

But I and others, who are right-minded Christians on all points, are assured that there will be a resurrection of the dead, and a thousand years in Jerusalem, which will then be built, adorned, and enlarged, [as] the prophets Ezekiel and Isaiah and others declare.

…And further, there was a certain man with us, whose name was John, one of the apostles of Christ, who prophesied, by a revelation that was made to him, that those who believed in our Christ would dwell a thousand years in Jerusalem; and that thereafter the general, and, in short, the eternal resurrection and judgment of all men would likewise take place.

Justin Martyr
Dialogue with Trypho
Chapter LXXVII & LXXXI

Only two advents of Christ

Of these and such like words written by the prophets, O Trypho,” said I, “some have reference to the first advent of Christ, in which He is preached as inglorious, obscure, and of mortal appearance: but others had reference to His second advent, when He shall appear in glory and above the clouds; and your nation shall see and know Him whom they have pierced, as Hosea, one of the twelve prophets, and Daniel, foretold.

Justin Martyr
Dialogue with Trypho
Chapter XIV

Only two advents. Resurrection and Hell.

For the prophets have proclaimed two advents of His: the one, that which is already past, when He came as a dishonored and suffering Man; but the second, when, according to prophecy, He shall come from heaven with glory, accompanied by His angelic host, when also He shall raise the bodies of all men who have lived, and shall clothe those of the worthy with immortality, and shall send those of the wicked, endued with eternal sensibility, into everlasting fire with the wicked devils.

Justin Martyr
First Apology
Chapter LII