What are the detail of the character of the immortal strulburgs?

They are born to "normal" parents and are marked by a dot above the left eyebrow that changes color as they grow older until the dot turns completely black at age forty. Really, Swift asks if we would actually like to live forever. Swift regards immortality as a sort of "living death." The Struldbrugs are depressed, perhaps because there is no reason to act quickly. They have all the time in the world. Meanwhile, they have plenty of time to see what mortals have done for themselves and their society in their fleeting time alive.