We know the story, Luke describes the scene. We find it in Luke 23 starting with verse 23:
“ 33 And when they were come to the place, which is called Calvary, there they crucified him, and the malefactors, one on the right hand, and the other on the left.34 Then said Jesus, Father, forgive them; for they know not what they do. And they parted his raiment, and cast lots.35 And the people stood beholding. And the rulers also with them derided him, saying, He saved others; let him save himself, if he be Christ, the chosen of God.36 And the soldiers also mocked him, coming to him, and offering him vinegar,37 And saying, If thou be the king of the Jews, save thyself.38 And a superscription also was written over him in letters of Greek, and Latin, and Hebrew, THIS IS THE KING OF THE JEWS.39 And one of the malefactors which were hanged railed on him, saying, If thou be Christ, save thyself and us.40 But the other answering rebuked him, saying, Dost not thou fear God, seeing thou art in the same condemnation?41 And we indeed justly; for we receive the due reward of our deeds: but this man hath done nothing amiss..”

Matthew confirms what the passerby’s were saying, in Matthew 27:38-40:
“38 Then were there two thieves crucified with him, one on the right hand, and another on the left. 39 And they that passed by reviled him, wagging their heads, 40 And saying, Thou that destroyest the temple, and buildest it in three days, save thyself. If thou be the Son of God, come down from the cross.”

The scene is laid out in SOP (Desire of Ages):
“To Jesus in His agony on the cross there came one gleam of comfort. It was the prayer of the penitent thief. Both the men who were crucified with Jesus had at first railed upon Him; and one under his suffering only became more desperate and defiant. But not so with his companion. This man was not a hardened criminal; he had been led astray by evil associations, but he was less guilty than many of those who stood beside the cross reviling the Saviour. He had seen and heard Jesus, and had been convicted by His teaching, but he had been turned away from Him by the priests and rulers….. On the cross he saw” the wagging heads. He heard the taunt taken up by the other: "If Thou be Christ, save Thyself and us." But he also hears many defending Jesus and tell of His many works. The conviction comes back to him that this is the Christ. Turning to his fellow criminal he says, "Dost not thou fear God, seeing thou art in the same condemnation?" The dying thieves have no longer anything to fear from man. But now presses the conviction of all he is seeing and hearing and he says, "And we indeed justly, for we receive the due reward of our deeds: but this Man hath done nothing amiss." Luke 23:41.
The thief now is brought by the Holy Spirit to confess his faith, and take hold of the opportunity before him. SOP tells us:

“The Holy Spirit illuminates his mind, and little by little the chain of evidence is joined together. In Jesus, bruised, mocked, and hanging upon the cross, he sees the Lamb of God, that taketh away the sin of the world. Hope is mingled with anguish in his voice as the helpless, dying soul casts himself upon a dying Saviour. "Lord, remember me," he cries, "when Thou comest into Thy kingdom." The Desire of Ages, 749, 750.

The thief took hold of the opportunity before him and brought forth "fruits" of the Spirit. Ellen White states that "repentance for sin is the first fruits of the working of the Holy Spirit in the life."—The SDA Bible Commentary, Ellen G. White Comments, on Rom. 2:4, p. 1068.!
His pardon came quickly: the words of Jesus were soft, full of love, compassion, and power; “Verily I say unto thee today, Thou shalt be with Me in paradise....” and hearing the answer, the thief had a peace that comes with the recognition of his acceptance with God.

After Christ's death the thief was still alive. Therefore, a short time was allotted him in which to grow in grace and sanctification. Although the Bible is silent regarding any further works of witnessing and spiritual growth during his short "lifetime" in sanctification, from Christ words we can be sure his works did follow him. For with the Spirit of Christ dwelling in his heart, he could not but be Christlike during the remaining hours of his life and, by his life, witness for Christ right up to his last conscious moment. Sanctification is the work of a "lifetime," be it long or short. And after his conversion, the "lifetime" of the penitent thief was "short." What is your allotted time, something to think about.