The Tucks view immortality quite differently from the rest of the world because they are experiencing it. It is one thing to want to live forever, another thing entirely when it happens to you. As they watched the world around them change (not always for the better) and as they lose those individuals whom they care about (because they age and the Tuck's do not) they gained a different perspective on immortality, one which Winnie comes to understand through her own close relationship to the Tucks. We often long for things (such as everlasting life) because they have a certain allure - we think that they will make our lives better, when in reality the opposite is often the case. When you are immortal, you don't get to experience the intense array of feelings and emotions that those individuals who understand life as fleeting experience daily.This is what Winnie comes to understand through her connection to them.
Jesse, too, has a view on immortality that is colored by what he feels for Winnie. He longs to be like her, and she, at first, longs to be immportal so that she can be with him. Ultimately, what she learns from the Tucks is that life is far too valuable to throw away on immortality.
The man in the yellow suit represents capitalism - the idea that everything in life has a value, including life itself. He wishes to gain personally and monetarily through the bottling and selling of immortality. This is a recurring theme in literature and in history as well as in science - the search for the "fountain of youth." Today, we see "youth" sold in bottles - anti-aging creams, vitamins that promise to restore vitality. This is a major enterprise, and the man in yellow is representative of it.
In the book Tuck Everlasting Winnie is taken to the home of the Tucks deep in the forest on her family's property. Winnie learns about the Tuck's who have drank from a spring that resulted in them having everlasting life and health.
Angus Tuck defines life as a wheel that should continue to turn. He says the wheel for the Tucks no longer turns. He dreams of dying because he feels that living forever is not a good thing at all.
In a conversation with Winnie he shares that many people long for the idea of living forever. It is the reason he does not want the well exposed because if they do they do beginning drinking from it, he feels they will have regret and the wheel of life will stop turning.
For the man in the yellow suit, the idea of the spring is a commercial venture. He knows that people will come to buy the water in order to preserve themselves.
"If there's one thing I've learned about people, it's that many will do anything, anything not to die. And they'll do anything to keep from living their life." (Angus Tuck)
"Immortality isn't everything the preachers crack it up to be." (Miles Tuck)