According to the Jaimini Sutras longevity can be determined by looking at the placement of the lords of the first and eighth houses. If both are in either movable (Aries, Cancer, Libra, Capricorn) or dual (Gemini, Virgo, Sagittarius, Pisces) rāśis the native will have longevity. If both are in dual rāśis or if one is in a movable and the other in a fixed (Taurus, Leo, Scorpio, Aquarius) rāśi the native will have moderate longevity. If, however, both of these graha are in fixed signs the native will have a short life. These rules can be applied to either 1 or 8 from the lagna or from Chandra.1
Clearly, the idea here is that the graha calling the shots in bhavas of the self and change must be under the influence of a sign which makes it movable. If too much of a stationary, tamasic energy is in a house which requires the individual to change and adapt to life the person will have a problem adapting. The more of a movable personality or response one has in relation to the self and the uncontrollable or unexpected changes of life the better suited he/she will be to keeping up with life and remaining on one’s toes.
Looking at the condition of the eighth house should also be a good significator of longevity, as well as the condition of Śani (Saturn).
Jaimini Sutras. Adhyaya II, Pada 1. ↩