Here's the text in the NIV:

10 The Lord said, “What have you done? Listen! Your brother’s blood cries out to me from the ground. 11 Now you are under a curse and driven from the ground, which opened its mouth to receive your brother’s blood from your hand. 12 When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth.”

13 Cain said to the Lord, “My punishment is more than I can bear. 14 Today you are driving me from the land, and I will be hidden from your presence; I will be a restless wanderer on the earth, and whoever finds me will kill me.”

15 But the Lord said to him, “Not so; anyone who kills Cain will suffer vengeance seven times over.” Then the Lord put a mark on Cain so that no one who found him would kill him. 16 So Cain went out from the Lord’s presence and lived in the land of Nod, east of Eden.

KJV text:

11 And now art thou cursed from the earth, which hath opened her mouth to receive thy brother's blood from thy hand;

12 When thou tillest the ground, it shall not henceforth yield unto thee her strength; a fugitive and a vagabond shalt thou be in the earth.

13 And Cain said unto the Lord, My punishment is greater than I can bear.

14 Behold, thou hast driven me out this day from the face of the earth; and from thy face shall I be hid; and I shall be a fugitive and a vagabond in the earth; and it shall come to pass, that every one that findeth me shall slay me.

15 And the Lord said unto him, Therefore whosoever slayeth Cain, vengeance shall be taken on him sevenfold. And the Lord set a mark upon Cain, lest any finding him should kill him.

16 And Cain went out from the presence of the Lord, and dwelt in the land of Nod, on the east of Eden.

I find absolutely no mention of extended life for Cain, except that God would punish anyone who killed him. However, in this battle God doesn't exist, so that part is irrelevant.