A correct metric to define life span!!
If for a moment we try to abstract the concept of time and assume that there is a 4th dimension of space and we are constantly moving across the fourth dimension. Imagine a particle placed on paper. The particle is free to move in the dimension of the paper (2D dimension). Let us say an external force tries to move the paper along the 3rd dimension (height), then the particle will see different variations of the 2D space as different instances. The particle can conveniently attribute the concept of time to the changing nature of the 2D space. Now for a moment assume that the external moving force, which moved the particle in the 3rd dimension stopped acting. If this happens, the particle would stop having the perception of time and would assume that it is at the same time instance. Remember that the external force is responsible for every change occurring in the 2D space. That is to say, if the particle were to be replaced by an organism, and assuming that the external force is also responsible for changes in the organisms body, absence of the external force would mean complete time stop for the organism.
How can we leverage the above concept? A simple logical extension of the fact that we are constantly moving across the fourth dimension would be the freedom to change the speed of movement. Yes, I mean whether can we change the rate at which we traverse the 4th dimension. If we think in these terms, the lifespan of an organism should be the length traversed across the fourth dimension and not the quantity of time spent. That is to say, the thing which we should focus on is distance traversed across 4th dimension which is velocity * time. And also, it should be considered that a person who has traversed more across the 4th dimension has lived more than a person who has spent more time but traversed lesser. Now, if we were to assume for simplicity that rate at which time passes is same for everyone (physics shows this is not the same), then the variable which we can control is the speed. Thus giving us a control over the length traveled across the fourth dimension.
As in physics, a particle who travels more in a given amount of time is considered to have covered more distance, similarly, the metric to measure the speed across 4th dimension should be the amount experienced. That is to say, an organism who experiences more in the same amount of time should be considered to have traveled more across the 4th dimension than an organism who has experienced lesser. As a logical extension, even though both organisms have spent an equal amount of time traversing the 4th dimension, one has traveled farther than the other. Luckily the 4th dimension is not a space dimension, otherwise, the organisms would not meet, being at different points on that axis. This I feel is an important concept which can guide how we lead our lives. Assuming that the goal of life is to travel maximum along the fourth dimension, experiencing more every day would make sense. To put it simply we should always aim to increase the speed at which we travel. However, an interesting argument would be what if the goal is not to traverse the maximum across that dimension? I think that too is completely fine, but then the individual will have to define a metric for himself. The metric definition is of utmost importance because it directly is a measure of the worth of life and happiness. In the absence of metric, it would be an unguided journey.
So now I know that I have to increase my speed along the 4th dimension!!!!!!!