Enneads I.5: Does Happiness Increase With Time?
Length of Happiness Does Not Affect Its Quality
5. Would equal happiness be predicated of three men, one who had been happy from his life's beginning to its end, the other only at its end, and the third, who had been happy, but who ceased being such.[55] This comparison is not between three men who are happy, but between one man who is happy, with two who are deprived of happiness, and that at the (present moment) when happiness (counts most). If then one of them have any advantage, he possesses it as a man actually happy compared with such as are not; he therefore surpasses the two others by the actual possession of happiness.
IF UNHAPPINESS INCREASE WITH TIME, WHY SHOULD NOT HAPPINESS DO SO?
6. (It is generally agreed that) all calamities, sufferings, griefs and similar evils are aggravated in proportion to their duration. If then, in all these cases, evil be increased with time, why should not the same circumstance obtain in the contrary case? Why should happiness also not be increased?[56] Referring to griefs and sufferings, it might reasonably be said that they are increased by duration. When, for example, sickness is prolonged, and becomes a habitual condition, the body suffers more and more profoundly as time goes on. If, however, evil ever remain at the same degree, it does not grow worse, and there is no need of complaining but of the present. Consideration of the past evil amounts to considering the traces left by evil, the morbid disposition whose intensity is increased by time, because its seriousness is proportionate to its duration. In this case it is not the length of time, but the aggravation of the evil which adds to the misfortune. But the new degree (of intensity) does not subsist simultaneously with the old, and it is unreasonable to predicate an increase as summation of what is no more to what now is. On the contrary, it is the fixed characteristic of happiness to have a fixed term, to remain ever the same. Here also the only increase possibly due to duration of time depends on the relation between an increase in virtue and one in happiness; and the element to be reckoned with here is not the number of years of happiness, but the degree of virtue finally acquired.