Longevity

[Job 8:9] (For we are but of yesterday, and know nothing, because our days upon earth are a shadow:)
[Of yesterday - that is, a recent race, He perceived that Job had no opinion of their abilities, but thought they knew little. It is evident that Bildad refers to those times in which human life was protracted to a much longer date than that in which Job lived; when men, from the long period of eight or nine hundred years, had the opportunity of making many observations, and treasuring up a vast fund of knowledge and experience. In comparison with them, he considers that age as nothing, and that generation as being only of yesterday, not having had opportunity of laying up knowledge.
A shadow - (Ps 144:4), nor could they expect it, as their days upon earth would be but a shadow, compared with that substantial time in which the fathers had lived. Perhaps there may be an allusion here to the shadow projected by the gnomon of a dial, during the time the sun is above the horizon. As is a single solar day, so is our life. The following beautiful motto I have seen on a sundial: "We are shadows!" referring to the different shadows by which the gnomon marked the hours, during the course of the day; and all intended to convey this moral lesson to the passengers: Your life is composed of time, marked out by such shadows as these. Such as time is, such are you; as fleeting, as transitory, as unsubstantial. These shadows lost, time is lost; soul lost! The writer of this book probably had before his eyes these words of David, in his last prayer, 1 Chronicles 29:15: "For we are strangers before Thee, and sojourners, as all our fathers were; our days upon earth are as a shadow, and there is no expectation. There is no reason to hope that they shall be prolonged; for our lives are limited down to threescore years and ten, as the average of the life even of old men."
The days of this life are like a "shadow", dark and obscure; full of the darkness of adversity and trouble, as well as greatly deficient in the light of knowledge; there is nothing in them solid and substantial. The greatest and best things of this life are but a vain show; in heaven there is a better and more enduring substance: every thing is mutable and uncertain here. Man is subject to a variety of changes in his mind and body, in family and outward estate and circumstances: and life itself is but a vapor, which appears a while and soon vanishes away; or rather like a shadow, that declines, is fleeting, and quickly gone
Reader take heed! We know nothing as compared with them because of the shortness of our lives; so even Jacob (Gen. 47:9). Knowledge consisted then in the results of observation, embodied in poetical proverbs, and handed down by tradition. The more we think we know, the less we find we really know, life is a learning process.
Longevity gave the opportunity of wider observation.]