I imagine that by the time Lucent leaves Sharlayan (shortly after Endwalker) he's a full sage, and that the process of becoming a sage takes approximately as long as becoming a doctor IRL. so, he's been living there like thirteen years, give or take a few? and he came to Sharlayan as an adult after living some indeterminate number of years as a Wood-Warder

...so, how old is he? I have no fucking clue, and neither does he

Doing some Old Sharlayan sidequests for The Lore, and discovered this tidbit

thinking about how SGE!Lucent, despite being cis, ended up a trans metaphor after all

namely, he is not comfortable in his body unless he is continuously changing it to better suit him, including in ways that would be considered "risky" and "bizarre" to many people. the fact that doing so often has him straining against the limits of his vessel is a plus. it makes him feel alive, to press up against those boundaries and transcend them - those flashes of clarity, the euphoria of triumph. he may die or drive himself to madness in the process, but it's better than suffocating slowly in the shackles of his flesh.

it's a happy arrangement that his profession synergizes with his personal research - a lot of what he figures out from experimenting on himself helps him figure out how to help others, and a lot of what he learns in the process of expanding his medical knowledge goes right back into his experimentation. and he does genuinely care a lot about helping other people! he believes very strongly in What It Means To Be A Healer! so strongly that he's gotten into more than one fight about it

(his friends don't dissuade him from experimenting, but they do try to get him to do it in safer ways. e.g. "please do not lock yourself inside a remote cave and drink an experimental and potentially deadly tincture For Science. at least let one of us stay with you and maybe also double-check your manic midnight calculations")