Though this long life prayer must have been conducted ages ago. I'd like to add onto this thread that in our daily sadhanas, we also request Dorje Shugden to increase our Guru's life by merit of our commitments to the Guru and protector. It says here like this:
"The stainless sun of Je Tsongkhapa’s tradition
Shines throughout the sky of samsara and nirvana,
Eliminating the darkness of inferior and wrong paths;
Please cause its light to spread and bring good fortune to all living beings.
May the glorious Gurus who uphold this tradition
Have indestructible lives, as stable as the supreme victory banner;
May they send down a rain of deeds fulfilling the wishes of disciples,
So that Je Tsongkhapa’s doctrine will flourish."
It is important that we constantly remember our Lama's kindness for he is the one who has spent his entire life to bring us to newer levels which we have never been and in their loving compassion for us, showered us with the nectar of Dharma. Hence, through our daily conduct, whether or not our Lama is around us, we should put our body, speech and mind altogether to align ourselves together with our Lama's three secrets.