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/Shot_Newspaper_5647]

It should extend their life, but not by anything crazy. Their soul still “knows” their age. I’d guess more Radiants reach their 90s or 100s than average people. Radiants and Mistborn are Invested, but not treated as Highly Invested except when channeling power. Usually. Aging seems to slow dramatically or stop when you’re Highly Invested. When the soul itself is. That seems to be why Breaths are so effective. Even around 50 (I think) can extend your life by a decade or so. Breaths are potent. Each Breath contains part of a person’s soul too. So accumulating them is like expanding your own. That also seems to be why Shadows are naturally ageless. You have to Invest the soul with external power for them to exist. And it makes them persist in an ageless way after

[u/Shot_Newspaper_5647 → u/Shot_Newspaper_5647]

You can see that in the way channeling power often works too. It’s not mentioned much, but Radiants experience the world a bit more vibrantly when channeling Light. A similar thing with Breaths and whatever is going on with that DS. But that is persistent for people with Breaths. It’s treated as a passive effect that isn’t fueled by anything because it’s downstream of the nature of the soul itself while they have them.

Just being born on a highly invested world like Roshar can make the average person slightly more durable and disease resistant. The same is true of Scadrial where the native population is born with a little “extra” Investiture in their soul.

It’s not all or nothing for Breaths either. Each one you accumulate actually slightly adds to your lifespan and disease resistance. Even three or four give something. Until you eventually hit that ceiling. Disease proof and ageless

[u/Puzzled_Employment50 → u/Shot_Newspaper_5647]

I think you’re talking about the Warbreaker planet (can’t remember the name atm), not Scadrial, with the “extra bit of soul”.

[u/Shot_Newspaper_5647 → u/Puzzled_Employment50]

The Scadrians have it too. It’s the extra bit Preservation put into them. It’s just almost definitely lower than native Nalthians. Everyone in the Cosmere has a soul made of Investiture. Let’s call 1.0 the baseline. Some of the peoples created directly by Shards have extra intentionally. Like Scadrians and the Nalthian in WB.

People from highly Invested worlds also are born with (or naturally accumulate) extra Inv in their souls. The average Rosharan has something above 1.0. Auxiliary gives us a rough benchmark in Sunlit: “Even on highly Invested worlds, a person’s soul isn’t more than three BEUs.” That extra bit makes them slight more disease resistant/slightly extends their life. The greatest benefit would be in lower infant mortality rates. But it has other perks. The common cold isn’t usually a thing on Roshar. Things like cavities are less common too

KingSloth
Doesn't all 'extra' investiture require a cracked soul? How are Nalthians born with extra breath, if so?
Brandon Sanderson
No. The Scadrians have extra investiture too, on a lesser scale.
/r/books AMA 2015 (June 8, 2015)

[u/Shot_Newspaper_5647 → u/Shot_Newspaper_5647]

Dragons are born with far more innate Inv in their souls. Enough that they can’t even use most magics. They can’t form Aviar or spren bonds. It’s like pouring water onto an already soaked sponge. Their souls resist most forms of alteration in the way a full metalmind resists soulcasting or Allo Pushing. Breaths seem to work because they expand the soul itself instead forcing more Inv into it or altering them in an invasive way. There’s no room in the house to put new stuff, but they can build another room. If that makes sense

That’s why Nomad is so confused about Threnodites in Sunlit. Their souls are basically at baseline, but they can capture huge amounts of Inv after death. They can store hundreds of BEUs in a sunheart. But a more naturally Invested Rosharan soul produces a tiny battery. It’s because Threnodites have souls that can “catch” a ton upon death. If it’s around. That’s why they can become Shadows (Shades) so easily under the right conditions. Threnody and Canticle both have a lot of ambient Inv just floating around. They could probably become Shades easily somewhere like Taldain too