Please elaborate on why the Struldbrugs lament the perpetuity of their lives.
Gulliver assumes that immortality would give him the opportunity to amass more money, to "excel all others in Learning," and to become a walking, talking encyclopedia of knowledge because he would have seen so much. However, the Struldbrugs are not happy about living forever because their lives are totally miserable.
They are typically pretty normal until they reach the age of thirty, and then they grow "melancholy and depressed," a condition which worsens as they age. They remain living, but they do not remain young, and this is the key to their misery. They grow more irritable, greedy, depressed, and self-centered as time passes. Once they reach eighty years old, they are declared dead under the law, their property passes to their children, and they are able to retain only a small portion of their fortunes (or they are supported by the public if they are poor, a fact for which they are resented). Moreover, because language changes, they eventually can no longer understand anyone around them and they live "like Foreigners in their own Country." Finally, they are "despised and hated" by everyone. It is not the educational opportunity Gulliver imagines it to be.