It appears that human beings and asuras are subject to death, whereas demigods are not. The demigods who reside with Lord Brahma in Satyaloka go to Vaikunthaloka in their present bodily constructions at the time of the dissolution. Therefore although Hiranyakasipu had undergone severe austerities, Lord Brahma predicted that he had to die; he could not become immortal or even gain equal status with the demigods. The great austerities and penances he had performed for so many years could not give him protection from death. This was foretold by Lord Brahma.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 03 – Text 21