In fact, natural death does not hunt and haunt or scare and scar the people of the Avesta, whether they belong to the Gathic period or not. The life, in the Yasna, Vispered, Yashts, and other existing parts of the Avesta, with the exception of the Vendidad, a later priestly addition to Zoroastrian scriptures, is not interrupted by death. It is the ills of society that challenge the Gathic people and make them determined to eradicate them all. What they aspire for and practice is a happy progressive life, both mental and physical or to use the current terms, spiritual and material, with Ahura Mazda, God Wise, as the final goal. The Gathic and relevant Avestan texts speak of the soul as if it were in a living body and not of a departed person.
Life is continuity.
Perhaps that is the reason why the ancient Zarathushtrians celebrated their birthdays but did not mourn the death-days of their dear ones. His death is not eulogized at all. The Gathas recommend one to extol persons during their lifetime and after. The Gathas are our guardians and protectors. They are food for our minds, in fact, food and clothing for our souls.