How does being an allomancer let you last longer as a cognitive shadow?

[Trusk'our Ghostblood]

In Mistborn Secret History, Preservation mentions to Kelsier that both allomancers and feruchemists will last longer than a normal person, as they are more invested than a regular human. This is a bit confusing to me, because Brandon has said before that allomancers aren't particularly invested when they aren't currently burning a metal. So does this mean that an allomancer only stays a bit longer in the cognitive realm after dying if they were burning a metal when they died? Or is it the potential to become invested, the Connection to Preservation, that makes them last longer?

As to another question I had in regards to becoming a cognitive shadow, do the bio-chromatic breaths that an awakener holds transfer with them to the cognitive realm when they die, and stay with them until they either find a way to come back as cognitive shadow or move to the Beyond? Or since they are primarily in the physical realm, they simply disperse? If an awakener were to come back as a returned, do they retain their breaths?

[Dancer Arbiter]

long exposure to Investiture will expand your soul. This is what lets beings linger in the Cognitive realm after they die. If you can expand your soul enough you will have the option stay permanently hence becoming a cognitive shadow.

Edited December 12, 2021 by Dancer

[Frustration Sliver]

any investiture will let you presist longer.

[Honorless Lord Ruler]

But Allomancers are still more Invested than normal humans, they do still have more base Investiture in their Spiritweb, even though it's not a lot and what they use mostly comes directly from Preservation, that's still something. And it's enough to give them a few more minutes. Plus, that connection means that they have channeled a lot of power and that has fundamentally changed their Spiritweb - that's how Slivers are said to work as per Brandon, Slivers can become Cognitive Shadows because their Spiritweb has been stretched by holding an entire Shard. Allomancers haven't held an entire Shard but they have held some quantity of Investiture multiple times in their lives. That would have an effect.