If a person aligns with the truth completely and achieves Arhatship, he does not have circumstances to teach others neither any responsibility(taking care of child, old parents, etc,) then he will simply pass away. Clinging to body/formation and survival is of no use after one's mind is purified of ignorance, desire and hatred(all attachments dropped). The person will simply exit formation/body into parinibbana(full release). End of the cycle, end of the suffering.