What's the noun for agelessness? Here's the word you're looking for.
age
The whole duration of a being being alive, whether animal, vegetable, or other kind
The amount of full years/months/days/hours etc. which someone, or something, has been alive
(uncountable) That part of the duration of a being or a thing which is between its beginning and any given time; specifically the size of that part.
(uncountable) The latter part of life; an advanced period of life, eld; seniority; state of being old.
(countable) One of the stages of life
(uncountable)Mature age; especially, the time of life at which one attains full personal rights and capacities.
(countable) The time of life at which some particular power or capacity is understood to become vested.
(countable) A particular period of time in history, as distinguished from others.
(countable) A great period in the history of the Earth.
(countable) A century; the period of one hundred years.
The people who live at a particular period.
(countable) A generation.
(countable, hyperbolic) A long time.
(poker) The right of the player to the left of the dealer to pass the first round in betting, and then to come in last or stay out; also, the player holding this position; the eldesthand.
“An agemate of Miriam's could say, 'it looks like she doesn't respect her brother', 'it looks like' being a literal and significant component of the agemate's criticism.”
“In the meantime, their husbands are at work or idle with their agemates.”
“And playing off a line from Finn, it's not obvious to me that American students are so much farther down the intelligence scale than their agemates in other lands.”
“Starring Eric Idle as a director, it portrays everyone in Hollywood as either effete New Agers or venal bullies.”
“We'll be hearing from a few people who would definitely be classed as New Agers, but with a bent for ecological activism.”
“The third photograph is of a retired railway man who took up a new life as a volunteer in a museum in Austria staffed almost entirely by third agers.”