"it is true that the invisible grace that these structures communicate to us, or for which they are the occasion of our reception, will perdure even after they cease. However, in a sense, just the inverse is true as well: invisible grace moves us toward the sacraments not as mere historically contingent means, but also as precursors to a more profound eschatological form of dependence upon mediation: the mediation of the sacred humanity of Christ, which will perdure eternally. The sacraments are imperfect instrumental applications 'already' of what we will experience more perfectly for eternity: dependence upon the mediating grace of Jesus Christ as man. . . .
"in contrast to Rahner's view, sacramental grace for Aquinas is not simply the visible manifestation of what is always, already happening invisibly outside the Church. Nor does extra-sacramental grace drive us towards the sacraments simply because of a general human need for categorical mediation. Rather, such grace 'outside the Church' is only a diminished form and anticipation of what comes to full reality uniquely in the sacraments of the Church. Quite in opposition, then, to Rahner's view, sacraments cannot appear as visual aids to what we already possess, but they are instruments that incorporate us into a higher form of life with God than that which we previously possessed when we were not yet incorporated into the fullness of sacramental life.
". . . Like Congar, St. Thomas certainly holds that the sacraments are the means of grace that produce an inward spiritual communion and that they give way eventually to the eschatological life of the kingdom of God. He also makes it clear, however, that these same sacraments are part of the inherent common good of social communion into which the invisible workings of grace invite us, and by which those same workings are inwardly maintained. Nor does this corporate body cease to be eschatologically. When these sacramental means cease to exist, they do so in order to give way not to a non-sacramental, invisible reality, but to a superior communal life that is itself also visible and invisible. This is the life of the Resurrection, in which we will live in everlasting dependency upon the 'sacramental' mediation of Christ himself: the human mediation of the Savior as High Priest. His humanity will remain the everlasting instrument and sign of the communication of divine life, such that we will be dependent upon Jesus as both God and human for eternity. Already in the life of the Church in this world, then, sacramental communion is part of the very form of the saving life of grace, since we are saved in an ecclesial body that is inseparably visible and invisible."
Thomas Joseph White, O.P., "The priesthood makes the Church: ecclesial communion and the power of the keys," Nova et vetera: the English edition of the international theological journal 9, no. 1 (Winter 2011): 221, 227-228 (209-236).