Eternal life involves quality of existence more than duration. Indeed, in Heaven we shall be far more concerned with how well we are living than how long.
"This is life eternal, that they might know Thee the only true God, and Jesus Christ who Thou hast sent" (John 17:3).
Born again believers in the Lord Jesus Christ presently "have eternal life" (I John 5:13). We are united with life Himself, that is, with the Lord Jesus who declared, "I am... the life" (John 14:6). "To live is Christ" echoed the Apostle Paul, and thus believers exist not only in the physical and temporal environment of our earthly perception, but in the transcendent life of God Himself (Philippians 1:21). In a limited sense, eternity has already begun for us, and our Lord calls us to a quality of existence that even now bears the atmosphere and fragrance of Heaven.
We experience and express such glorious potential by faith. "If ye then be risen with Christ, seek those things which are above, where Christ sitteth on the right hand of God. Set your affection on things above, not on things on the earth. For ye are dead, and your life is hid with Christ in God" (Colossians 3:1-3). Note Paul's present tense description of our being "risen with Christ," and of our life being "hid with Christ in God." Do we believe such glorious and seemingly unlikely truth? Do we actually possess the means to overcome the limitations of earth that would keep us bound to its surly bonds, as it were? Can we know joy when sorrow seems the only possible portion? Is peace possible when turmoil surrounds us? Can a broken heart become an open portal for Heavenly realities to flood our being with joy and wonder? The Bible resoundingly promises that we can, and that we will as we trust and submit to the eternal Life that already teems in our Christ-inhabited spirits.
Nothing can thwart the peace, assurance and joy of the heart whose gaze affixes upon the risen Lord Jesus. Nothing. "Thou wilt keep him in perfect peace, whose mind is stayed upon Thee, because he trusteth in Thee" (Isaiah 26:3). Certainly the winds of time and earth will ruffle our sails, and worldly waves will crash upon the bow of our ship, threatening to swamp us. But our Helmsman will keep us on course, and we will sail unhindered toward the destination He set for us. Eternity is that port to which we venture, and eternity is the current that escorts us there. Yes, Heaven has come to us in the person of Christ in order that we may one day go with Him to Heaven. To the degree we know, believe and affirm this Truth to be true will be the degree to which we experience the eternal quality of being and existence freely given to us by the "Christ, who is our life" (Colossians 3:4).
"We know that the Son of God is come, and hath given us an understanding, that we may know Him that is true, and we are in Him that is true, even in His Son Jesus Christ. This is the true God, and eternal life."
(I John 5:20).