No matter how expert a swimmer one may be, one cannot survive for long in a vast sea like the Pacific Ocean. Similarly, no matter how expert a materialist one may be, whether a karmī, jñānī, or yogī, one cannot survive forever amidst the tossing waves of saṁsāra. Indeed, all living entities are being tossed repeatedly from one life to the next, from one species to another. Many philosophers have sought relief from saṁsāra by cultivating knowledge, but no amount of mental speculation or Vedānta study will take one to the other shore of the ocean of saṁsāra. At best, a jñānī can come to know that all material life is suffering, and by further purification he can understand the spiritual oneness of all beings. But even that understanding does not bring ultimate relief. Liberation from the ocean of birth and death comes with direct surrender to the Supreme Lord, who personally frees the devotee from suffering. As Lord Kṛṣṇa states, "For the devotees I am the swift deliverer from the ocean of birth and death" (Bg. 12.7).
King Kulaśekhara recommends the constant chanting of God's names as the way out of saṁsāra. Of course, only one who has spontaneous love of God can continuously chant His holy names. Mechanical chanting cannot continue for very long. But even neophytes are advised to chant Hare Kṛṣṇa as much as possible to develop their taste for the holy names. A symptom of an advanced devotee is that he has nāma-gāne sadā ruciḥ, tireless attraction for chanting or singing the Lord's names.
The six Gosvāmīs of Vṛndāvana achieved the perfect state of attraction for the holy names, chanting and hearing almost twenty-four hours daily. Prabhupāda writes, "Of course, we should not imitate him [Rūpa Gosvāmī], but the devotees of the Kṛṣṇa consciousness movement must at least be very careful to complete their sixteen rounds, their minimum amount of prescribed chanting. Nāma-gāne sadā ruciḥ: we have to increase our taste for singing and chanting Hare Kṛṣṇa" (Teachings of Queen Kuntī, pp. 149-50).
Continuous chanting of the holy name with great relish (ruci) is the privilege of the advanced devotee, but one who chants with offenses is also recommended to chant constantly. As the Padma Purāṇa states, although in the beginning one may chant the Hare Kṛṣṇa mantra with offenses, one can free himself from those offenses by chanting again and again. Pāpa-kṣayaś ca bhavati smaratāṁ tam ahar-niśam: "One becomes free from all sinful reactions if one remembers the Lord day and night."
Whatever a person thinks of at the time of death determines his next life. This is another reason for chanting the holy names constantly. If we can chant at the difficult hour of death, we will guarantee our return home, back to Godhead, without a doubt.