The Incredible Hulk(s) - (She-Hulk, Red Hulk): while it has never been substantiated, the Hulk's near-perfect and instantaneous regenerative abilities should mean he will never appreciably age or will age incredibly slowly in relationship to other humans.
It is safe to assume all Hulks (red or green) will have the same nearly-immortal quality. It is unknown whether any of the Hulks will/do age while in their human forms.
The Hulk Recovers from Vector's devastating attack - Incredible Hulk vol. 2 #398
The mechanism for the Hulk's biological process has not been explained or developed so we are forced to determine how his biological process functions from examples shown in the comics. As the above example shows, the Hulk is able to regenerate from injuries that would kill ordinary humans. He is able to regenerate mass and repair tissue damage nearly instantaneously. This would give the impression he would have the ability to have a very long, if not immortal, lifespan.
As far as Banner's aging is concerned several theories have been forwarded over the decades in the Hulk's books, occassional What-If's, one shots, and alternative timelines. They include:
As Banner aged Hulk would simply stop turning into Banner after he grew too old to sustain himself effectively.
Banner is as immortal as the Hulk deriving his immortality from their shared cellular relationship
Banner dying physically, perhaps from a heart attack, and turns into the Hulk unable to return to his potentially human form.
What If/Alternative timeline Stories
What if scenarios do not exactly replicate the canon characters.
The goal of these stories function as a Gedankenexperiment (though-experiment) a method to extrapolate characters, ideas, themes outside of the canon universe.
If a representation of a character shows up with a power or ability not necessarily seen in the canon character it may be implied the canon character could have this ability but there is no guarantee.
Sometimes a comic company will adapt an idea or power from an experimental story and bring it to the canon universe, but it is done on a case by case basis.