The Tuck family feels that living forever makes them miss out on the human experience. Because they cannot age, they have to live apart from other people and can’t get to know anyone. The two younger Tucks, Miles and Jesse, can’t marry. None of the Tucks can have any serious relationships.
There are some benefits to living forever. Jesse and Miles travel and experience the world, and have the opportunity to see it change. Mae and Angus live comfortably, as they are experts at crafts they can sell to live off of. They live a mostly relaxed and quiet existence.
The Tucks do their best to prevent anyone else from finding out about the spring or accidentally drinking from it. It is hidden by pebbles. Winnie Foster only found out about it because she saw Jesse drinking from it. Since he was already immortal, it wouldn’t hurt to quench his thirst.
The Tucks kidnap Winnie to prevent her from drinking from the spring, and so they can tell her the whole story. They explain how everyone but the cat drank from the spring, and they later realized they could not be hurt or die. Mae Tuck tells Winnie this is why she should not drink from the spring.
"And we figured it'd be very bad if everyone knowed about that spring," said Mae. "We begun to see what it would mean." She peered at Winnie. "Do you understand, child? That water—it stops you right where you are” (Chapter 7).
Angus also explains that the Tucks have been removed from the normal wheel of life. This is what makes it a little tiring for them. They do not get to age and die like everyone else.
Jesse has a different perspective. He is the youngest Tuck, and never got to have a family like Miles because he was only seventeen when he drank. He knows he can’t marry a normal, mortal woman. Miles’s wife and children left him because they thought he was cursed by the Devil. Since Winnie knows about the Tucks, Miles asks her to wait until she is his age and then drink the water so they can get married, but she decides not to do so.
The Tucks return much later to learn Winnie lived a normal life and died at a respectable old age. They understand why she made the choice she did. Not everyone wants to live forever, and the Tucks wish they had known what was in that spring.