Give up family life timely to practice detachment

From Srila Prabhupada's purport to SB 4.28.3

When one reaches the age of fifty, he should give up family life. At that time one’s child should be grown up so that the father can leave the family responsibilities to him. The husband and wife may then go abroad to live a retired life and travel to different places of pilgrimage. When both the husband and wife lose their attachment for family and home, the wife returns home to live under the care of her grown-up children and to remain aloof from family affairs. The husband then takessannyāsa to render some service to the Supreme Personality of Godhead.

Sexual Addiction reduces life span, intelligence, opulence and personal beauty

Srila Prabhupada's Purport to 4.27.21

The great sage Nārada Muni was a naiṣṭhika-brahmacārī — that is, he never had sex life. He was consequently an ever-green youth. Old age, jarā, could not attack him. The invalidity of old age can overcome an ordinary man, but Nārada Muni was different. Taking Nārada Muni to be an ordinary man, the daughter of Time confronted him with her lusty desire. It requires great strength to resist a woman’s attraction. It is difficult for old men, and what to speak of young. Those who live as brahmacārīs must follow in the footsteps of the great sage Nārada Muni, who never accepted the proposals of Jarā. Those who are too much sexually addicted become victims of jarā, and very soon their life span is shortened. Without utilizing the human form of life for Kṛṣṇa consciousness, the victims ofjarā die very soon in this world.

Srila Prabhupada's purport to 4.28.1

When a man is young, he does not care for old age but enjoys sex to the best of his satisfaction, not knowing that at the end of life his sexual indulgence will bring on various diseases, which so much disturb the body that one will pray for immediate death. The more one enjoys sex during youth, the more he suffers in old age.

SB 4.28.6: 

When King Purañjana was embraced by Kālakanyā, he gradually lost all his beauty. Having been too much addicted to sex, he became very poor in intelligence and lost all his opulence. Being bereft of all possessions, he was conquered forcibly by the Gandharvas and the Yavanas.

Purport: 

When a person is attacked by the invalidity of old age and is still addicted to sense gratification, he gradually loses all his personal beauty, intelligence and good possessions. He thus cannot resist the forceful attack of the daughter of Time.

Svayambhuva Manu's happiness in giving his responsibilities to his son

SB 5.1.22: Svayambhuva Manu, with the assistance of Lord Brahma, thus fulfilled his desires. With the permission of the great sage Narada, he delivered to his son the governmental responsibility for maintaining and protecting all the planets of the universe. He thus achieved relief from the most dangerous, poisonous ocean of material desires.


Svayambhuva Manu took great satisfaction from abnegating the responsibility for ruling all the planetary systems of the universe. King Priyavrata had to be persuaded by Lord Brahma to accept the post of emperor of the entire universe. His father, Svayambhuva Manu, felt relieved to entrust the universal government to Priyavrata.

In the vedic culture one did their duty only for the purpose of satisfying the Supreme.When it was time to accept another duty they could very easily leave their current duty in the hands of someone else as they were not attached to the duty and its fruits , but attached to pleasing the Supreme.

Vanaprastha:Example of King Malayadhvaja and Queen Vaidarbhi

Reference Post for context: Activities of a Disciple in Separation from Spiritual Master

Srila Prabhupada's purport on vanaprastha life SB 4.28.45:

1. The wife especially should remain austere, not desiring luxurious dresses and living standards. She should accept only the bare necessities of life and minimize her eating and sleeping.
   
2. There should be no question of mating. Simply by engaging in the service of her exalted husband, who must be a pure devotee, the wife will never be agitated by sex impulses. The vānaprastha stage is exactly like this. Although the wife remains with the husband, she undergoes severe austerities and penances so that although both husband and wife live together, there is no question of sex. In this way both husband and wife can live together perpetually.
   
3. Nonetheless, the wife is expected to give up all luxurious habits. She should not even dress nicely or comb her hair. Hair combing is one of the main businesses of women. In the vānaprastha stage the wife should not take care of her hair. Thus her hair will become tangled in knots. Consequently the wife will no longer be attractive to the husband, and she herself will no longer be agitated by sex impulses.
   
4. In this way both husband and wife can advance in spiritual consciousness. This advanced stage is called the paramahaḿsa stage, and once it is obtained, both husband and wife can be actually liberated from bodily consciousness. If the disciple remains steady in the service of the spiritual master, he need no longer fear falling down into the clutches of māyā.

Example of King Malayadhvaja:

1. He was a powerful king and great devotee.
   
2. He was not attached when retiring from family life as we can see he divided his kingdom amongst his sons and then engaged in worship,executing austerities and following regulative principles in a solitary place(nirjana bhajan).SB 4.28.33
3. Practiced austerities and became equipoised in dualities.Austerities prescribed in the sastras help one transcend the material body.Sense control can be achieved automatically by engaging in the Lord's service. SB 4.28.37
4. He became fixed by following these principles for 36000 years.
   
5. He attained the perfection of life: Not only did he come to the conclusion that Krsna is everything but he also remained fixed in that realization.

Example of Queen Vaidarbhi:

1. She gave up all sensual enjoyment and in complete renunciation followed the principles of her husband, who was so advanced. Thus she remained engaged in his service.SB 4.28.43
2. Srila Prabhupada says in this regard:"If a woman is fortunate enough to be the wife of a pure devotee, she can serve her husband without any desire for sense gratification. If she remains engaged in the service of her exalted husband, she will automatically attain the spiritual perfections of her husband."
   
3. She remained austere, accepted only bare necessities of life, minimized her eating and sleeping and dressed in old garments.
4. While serving her husband the Queen did not even talk to her husband while serving.he would simply perform her prescribed duties without talk.This is evident from text SB 4.28.45
5. When she discovered her husband had left his body, she cried out of affection for him and she then prepared a blazing fire with firewood and placed the dead body of her husband upon it. When this was finished, she lamented severely and prepared herself to perish in the fire with her husband.SB 4.28.50