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THE PATH OF PERFECTION
Brahmaloka, there is still birth and death. The words  punar āvartinaḥ  mean “returning again,” or “repetition of birth and death.” We are changing bodies just as we change clothes, leaving one body and entering another. All planets are filled with living entities. We shouldn't think that only the earth is inhabited. There are living entities on the higher planets and lower planets as well. From our experience, we can see that no place on earth is vacant of living entities. If we dig into the earth, we find some worms, and if we go into the water we find many aquatics. The air is filled with birds, and if we analyze outer space, we will find many living entities. It is illogical to conclude that there are no living entities on the other planets. To the contrary, they are  full  of living entities.
In any case, Kṛṣṇa says that from the highest planet to the lowest planet, there is repetition of birth and death. Yet again, as in the former verse, He says,  mām upetya : “If you reach My planet, you don’t have to return to this miserable material world.” To stress this point, Śrī Kṛṣṇa repeats that upon reaching Goloka Vṛndāvana, His eternal abode, one is liberated from the cycle of birth and death and attains eternal life. It is the duty of human life to understand these problems and attain a blissful, eternal life that is full of knowledge. Unfortunately, people in this age have forgotten the aim of life. Why?  Durāśayā ye bahir-artha-māninaḥ  ( Bhāg.  7.5.31). People have been trapped by the material glitter—by skyscrapers, big factories, and political activities. People do not stop to consider that however big the skyscraper may be, they will not be allowed to live there indefinitely. We should not spoil our energy, therefore, in building great cities but should employ our energy to elevate ourselves to Kṛṣṇa consciousness. Kṛṣṇa consciousness is not a religious formula or some spiritual recreation but is the most important factor in our lives.
People are interested in attaining higher planets because there one's enjoyment is a thousand times greater and the duration of life much longer.
sahasra-yuga-paryantam   ahar yad brahmano viduh
The Path of Perfection
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rātriṁ yuga-sahasrāntāṁ  
 te 'ho-rātra-vido janāḥ  
    (Bg. 8.17)
The duration of the material universe is limited. It is manifested in cycles of  kalpas . A  kalpa  is a day of Brahmā, and one day of Brahmā consists of a thousand cycles of four  yugas , or ages: Satya, Tretā, Dvāpara, and Kali. The cycle of Satya is characterized by virtue, wisdom, and religion, there being practically no ignorance and vice, and the  yuga  lasts 1,728,000 years. In the Tretā-yuga vice is introduced, and this  yuga  lasts 1,296,000 years. In the Dvāpara-yuga there is an even greater decline in virtue and religion, vice increasing, and this  yuga  lasts 864,000 years. And finally, in Kali-yuga (the  yuga  we have now been experiencing over the past 5,000 years), there is an abundance of strife, ignorance, irreligion, and vice, true virtue being practically non-existent, and this  yuga  lasts 432,000 years. In Kali-yuga vice increases to such a point that at the termination of the  yuga , the Supreme Lord Himself appears as the Kalki-avatāra, vanquishes the demons, saves His devotees, and commences another Satya-yuga. Then the process is set rolling again. These four  yugas  rotating a thousand times comprise one day of Brahmā, the creator god, and the same number comprise one night. Brahmā lives one hundred of such “years” and then dies. These “hundred years” by earth calculations total 311 trillion and 40 million earth years. By these calculations, the life of Brahmā seems fantastic and interminable, but from the viewpoint of eternity, it is as brief as a lightning flash. In the Causal Ocean there are innumerable Brahmās rising and disappearing like bubbles in the Atlantic. Brahmā and his creation are all part of the material universe, and therefore they are in cons
In the material universe, not even Brahmā is free from the process of birth, old age, disease, and death. Brahmā, however, is directly engaged in the service of the Supreme Lord in the management of this universe; therefore he at once attains liberation. Elevated  sannyāsīs  are promoted to Brahmā's particular planet, Brahmaloka, which is the highest planet in the material