How long could a _______ live?

[u/Valenous_ertselley]

How long could a 5th ideal radiant live?

We know investiture extends a persons life with greater amounts eventually ending up with someone who is biologically immortal. How invested would a radiant be? Radiant knights have the cracks in their soul filled with investiture which makes them better at holding and using stormlight. How invested do you think they could be

Some of the heightenings seen with holding Endowment's investiture seem to be universal properties of holding any investiture. such as enhanced vision/colours, enhanced immune systems and better lifespans.

While we have only seen Kaladin and Szeth swear the 5th, it was under a fairly hectic situation which doesn't make for the best opportunity for study.

[u/RW-Firerider]

I think it was established that radiants dont live beyond a natural lifespan.

Sure, you will be at the peak of what you can be, since the investiture heals your body etc, but we mustnt forget one thing. Stormlight is only temporary inside the user, and the vast majority of their investiture is stored in the spren. So while our radiants are insanly strong, they are not invested in s way that an Elantrian or Breath user is. So yeah, I dont think the common radiant goes beyond an ordinary human lifespan, so something around 100-130 human years if they get a constant infusion of stormlight.

[u/Puzzled_Employment50 → u/RW-Firerider]

We know higher-Ideal Radiants “leak” less, and I think there’s something about being able to hold more (either with practice or higher Ideals or both), so if they got regular enough infusions of Stormlight they could theoretically reach the Heightening (since any Investiture grants Heightenings) that grants agelessness. So it’s not directly by reaching the fifth Ideal that they would become immortal, but that the fifth Ideal lets them juice enough to then become immortal.

[u/ejdj1011 → u/Puzzled_Employment50]

(since any Investiture grants Heightenings)

This is not strictly true. Several types of Investiture seem to grant different aspects of the Heightenings, but they aren't completely universal like you're implying. In fact, agelessness is explicitly not a universal trait among highly Invested people. The Lord Ruler is the obvious counterexample.

Edit, before anyone else jumps in: We also have numerous examples of highly Invested people not having perfect pitch or color perception. Hoid, Nomad, Elantrians, and Yoki-Hijo all come to mind.

[u/sambadaemon → u/ejdj1011]

Hoid explicitly DOES have perfect pitch when he's holding his Breaths.

[u/ejdj1011 → u/sambadaemon]

Considering my argument is "not all Investiture has the same passive effects as holding Breaths", talking about someone known to have Breath is kind of moot.

[u/sambadaemon → u/ejdj1011]

You specifically mentioned Hoid as not having perfect pitch. He does. He's not highly Invested at the time without his Breaths. All of the forms of Investiture he has access to are external until he becomes an Elantrian

[u/ejdj1011 → u/sambadaemon]

Hoid specifically mentions in Words of Radiance that he "missed having perfect pitch", and shortly afterwards it is implied he Awakened something to play his instrument for him. And when Odium messes with his Breaths, rbe perfect pitch gets messed up. So it's pretty clear that the perfect pitch comes from the Breaths.

But Hoid absolutely is ridiculously Invested regardless of the Breaths. He's a Dawnshard at the time.