In view of the admonition, "Go on unto perfection," you inquire,
"Should I go steadily onward, how soon may I expect to arrive at a state of perfection? And when I arrive at this point, will not the summit of Christian attainment be reached?"
Permit me to answer your latter inquiry first, and it will enable me more readily to meet the former.
The summit of Christian attainment reached? No, not in eternity itself, with receptive powers still growing, while immortality endures, will the attainments in love, knowledge, light, and power, which have been made possible through the atonement, be grasped. Paul says, "Not as though I had already attained, either were already perfect: but I follow after, if that I may apprehend that for which also I am apprehended of Christ Jesus. Brethren, I count not myself to have apprehended, but this one thing I do: forgetting those things which are behind, and reaching forth unto those things which are before, I press toward the mark for the prize of the high calling of God in Christ Jesus."
It is evident, as you perceive, on Scriptural authority, that a state of perfection which will not admit higher degrees is not to be expected. But that a state of perfection is attainable is most evident, and is proven upon the same premises. The apostle, in continuation of what I have already quoted, goes on to say, "Let us therefore, as many as be perfect, be thus minded;" including, as you observe, both himself and a part of those addressed as being in a state of perfection. I am the more particular in speaking of this subject, because it is not uncommon for those who oppose the doctrine of Christian perfection to refer to this passage.
Just the state of perfection aimed at in these passages (Phil. iii, 8-15) is what I would now urge upon you: that is, a state of perfection which requires progression — a state which could not even be retained, without obedience to "this one thing — forgetting those things which are behind and reaching forth unto those things which are before." The perfection to which your attention is urged, does not imply perfection in knowledge or light, but a state of supreme love to God, where all the powers of body and mind are perfectly subject to love's control, and ceaselessly offered up to God through Christ. This is Christian perfection; not angelic perfection, neither Adamic perfection, but Christian perfection. To think disparagingly of Christian perfection, implies, to my mind, thinking lightly of the atonement. To undervalue the efficacy of the blood of Christ to cleanse is sinful. And it would be sinful to doubt whether the offering presented to God, through Christ, is holy and acceptable.
What you need, in order to bring you into this state, is an offering up of yourself through this purifying medium. Now do you still ask, How soon may I expect to arrive at this state of perfection? Just so soon as you come believingly, and make the required sacrifice, it will be done unto you according to your faith. Christ came to take away our sin, to destroy the works of the devil, and to purge us from all iniquity. The purpose of man's redemption is not accomplished until he is presented perfect in Christ Jesus. When the Savior said, "It is finished!" then this full salvation was wrought out for you. All that remains is for you to come complying with the conditions, and claim it. As it has been purchased for you, it is already yours. If you do not now receive it, the delay will not be on the part of God, but wholly with yourself.
— from Faith and Its Effects (1848) VII.