Lord Buddha taught many methods to prolong our lives. Animal Liberation is a method commonly practised to extend our lifespan. When we practise giving medicine to the sick, giving of love and care to the elderly people, we can have healthy bodies and hence a longer life. Pureland practitioners as mentioned by Galen can control their death & rebirth in the Western Pureland by accomplishing the perfect recitation of Buddha Amitabha. Yidam practices of White Tara, Namgyalma, Amitayus & Tsongkhapa will extend our lifespan. A practitioner can control his death & rebirth to a Pureland if he had accomplished the highest yoga tantra practices of yidam like Vajrayogini, Yamantaka, Heruka and Guhyasamaja. Accomplished Powa practitioners can eject their minds from their bodies any time to the Pureland of a Buddha.
It is not the length of lifespan that really matters. It is the quality of our lives that we put to meaningful use e.g. benefiting others that matters. A person may have very short life but if that person had spent his entire short life benefiting others, he would have accumulated vast amount of merits for a better future next life. Someone may live very long in a present life but had never done anything virtuous or meaningful does not generate sufficient merits to ensure good future life.
Our mind travels from one realm of existence to another realm of existence upon expiry of our lifespan. Our mind will continue to experience the ordinary process of death and rebirth over and over again until we gain total liberation from samsara. In actuality our mind does not die. Dying here means the ordinary death. When we realize our mind cannot die, we should have no fear of dying. We should be concerned and fearful of our ordinary death instead. If we hadn’t trained and prepared for our ordinary death, we may end up taking a bad rebirth into the 3 lower realms of existence.
To conclude, we strive to purify our karma, accumulate merits and transform our mind as fast as possible until our gain liberation and enlightenment. We want to ensure we are in control of our ordinary death and rebirth along the journey to liberation and enlightenment.