When one person in a group or family holds on to a symbolic memory or experience with more importance than the other people involved in that experience or memory. For this person, a nostalgic benchmark holds a reference point for a significant event that is no longer significant to others who were involved in this experience or event.
A mother and son always go to a certain restaurant to eat chicken wings. As the son grows older, he no longer likes chicken wings and has no desire to eat them, but the mother insists on going back to the restaurant, which serves the chicken wings that both of them once loved. For the mother this is a nostalgic event, but for the son, who no longer eats chicken wings or likes them, this experience of going to the restaurant to eat chicken wings no longer holds any importance or nostalgia. So, for the mother this is a nostalgic benchmark, but for the son, it has no importance, or nostalgia, it has no benchmark anymore.