Why is defining the end-point criterion crucial for kinetic models?

Without a clear criterion, the mathematical output of the kinetic model remains abstract.

The concept of shelf life, even when derived from rigorous kinetic modeling, is inherently subjective because it relies on an externally defined measure of acceptability. The end-point criterion acts as the finish line for the mathematical calculation; if this criterion is vague—such as defining unacceptable taste subjectively—the precise numerical result generated by the kinetic model lacks practical meaning. Whether the standard is based on regulatory safety thresholds, a defined percentage loss of active pharmaceutical ingredient potency (like 10%), or consumer sensory panel rejection, that specific, agreed-upon metric is what translates the abstract calculation of degradation speed into a usable shelf-life declaration.