He'll live for one hundred years. So his twelve hours is millions of years. So still, he will die. Anything in this material world, it will not stay. Bhūtvā bhūtvā pralīyate (BG 8.19). Everything will be finished. Therefore even Brahmā's body is not eternal. What to speak of my body, your body, ant's body, his body... Sat. Sat means "that exists". Oṁ tat sat.
And cit. Cit means knowledge. So Kṛṣṇa's knowledge is perfect. Kṛṣṇa says, vedāham, vedāhaṁ samatītāni (BG 7.26). "I know past, present, and future." When Kṛṣṇa was questioned by Arjuna, Kṛṣṇa said that "Many millions of years ago, first of all, I spoke this science of Bhagavad-gītā or bhakti-yoga, to the sun-god." Imaṁ vivasvate proktaṁ vivasvān manave prāha. "I spoke, first of all, to Vivasvān, the Sun god." The Sun god's name is there, Vivasvān. Then Kṛṣṇa was questioned by Arjuna that "Kṛṣṇa, You and me, we are born very recently. How is that You say that You spoke to Sun god?