One can attain Kṛṣṇa consciousness or divine life at once, within a second—or one may not attain such a state of life even after millions of births. It is only a matter of understanding and accepting the fact. Khaṭvāṅga Mahārāja attained this state of life just a few minutes before his death, by surrendering unto Kṛṣṇa. Nirvāṇa means ending the process of materialistic life. According to Buddhist philosophy, there is only void after the completion of this material life, but Bhagavad-gītā teaches differently. Actual life begins after the completion of this material life. For the gross materialist it is sufficient to know that one has to end this materialistic way of life, but for persons who are spiritually advanced, there is another life after this materialistic life.
(Bhagavad-Gita----2:72----purport).

Similarly, regarding the haṭha-yoga system, which aims at the localized aspect of the Lord, Paramātmā, it has been experienced that many yogīs, such as Viśvāmitra, fall down. But bhakti-yogīs, once approaching the Supreme Personality of Godhead, never come back to this material world, as it is confirmed in the Bhagavad-gītā. Yad gatvā na nivartante: (B.G.15:6) upon going, one never comes back. Tyaktvā dehaṁ punar janma naiti: (B.G.4:9) after giving up this body, he never comes back again to accept a material body. Nirvāṇa does not finish the existence of the soul. The soul is ever existing. Therefore nirvāṇa means to end one's material existence, and to end material existence means to go back home, back to Godhead.
(Srimad Bhagavatam----3:25:29----purport).

Three words have been used in this connection to describe the achievement of Devahūti: ātmānam, brahma-nirvāṇam and bhagavantam. These refer to the gradual process of discovery of the Absolute Truth, mentioned herein as the bhagavantam. The Supreme Personality of Godhead resides in various Vaikuṇṭha planets. Nirvāṇa means to extinguish the pangs of material existence. When one is able to enter into the spiritual kingdom or into spiritual realization, one is automatically freed from material pangs. That is called brahma-nirvāṇa. According to Vedic scripture, nirvāṇa means cessation of the materialistic way of life.
(Srimad Bhagavatam----3:33:30----purport).

Nirvāṇa means the cessation of all material desires. Sometimes desirelessness is understood to imply an end to the workings of the mind, but this is not possible. The living entity has senses, and if the senses stopped working, the living entity would no longer be a living entity; he would be exactly like stone or wood. This is not possible. Because he is living, he is nitya and cetana—eternally sentient. For those who are not very advanced, the practice of yoga is recommended in order to stop the mind from being agitated by material desires, but if one fixes his mind on the lotus feet of Kṛṣṇa, his mind naturally becomes peaceful very soon.
(Srimad Bhagavatam----7:15:34----purport).