system
Given the following post, respond as if you're commenting on Reddit:
human
[Mistborn]Could a Feruchemist extend his life by spending it as a 70 year old?

Sazed mentions that the Feruchemical ability to store and draw on age is mostly used as a way to disguise oneself, since becoming older in order to become younger balances itself out.

But what if I'm a Feruchemist and I spend every day storing enough age to appear to be 70, and I do that all day, every day, until I'm actually 70?  Then, once I'm 70, I tap my stored power to appear 70, all day, every day, until I run out of stored power at about 130 years old?
gpt
Yes you could totally do this. The reason most don't is that it is quite difficult and isolating. Who wants to spend their twenties as a senior? You could totally do it, if simply extending your life was your primary goal, but that's not how many people live.

Feruchemists have always been rare, as has Atium, so not many people get the chance to do this, and those that have the chance may prefer to live in the moment.