Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
षष्ट्यब्दकेंद्रसौम्येभेष्टशुद्धे सप्ततिर्गुरौ ।मूलत्रिकोणगैः सौम्यैर्गुरौ स्वोच्चसमन्विते ॥ ११३ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 113.
That gives sixty years. Good planets may be in the corner houses, with the 8th clear: seventy years. Good planets may be in their mulatrikona (a planet's strong own-sign part), with Jupiter in his high sign. (Our text is unclear here: the word 'ibhe' and the first word 'gurau'.)
Simple meaning: Good planets in corner houses with a clear 8th give seventy years. Sixty and eighty come from other placements.
लग्नाधिपे बलयुतशीत्यब्दं त्वायुरीरितम् ।
Strong lagna lord with good planets well placed gives eighty years of life.
लयेशे धर्मगेजीवेष्टस्थे क्रूरेक्षिते जिताः ।
The lagna lord and 8th lord together in the 8th may shorten life to 27 years.
लग्नेऽशुभेज्यौ ग्लौदृष्टौ मृत्यौ कश्चन चाकृतिः ।
Some placements may shorten life to 22 years, others give long life.