I unfortunately can't cite the miqo'te lifespan thing, it's just something I heard in RP from a friend who generally has their facts straight RE: miqo'te lore. I kinda take their word on that and move on, because my interests are elsewhere.

Quote Originally Posted by EaraGrace View Post
My own conception of aetheric density is that while rejoining increases the density of one’s soul, the world itself still places those souls in bodies that remain 1/14 Sundered. We don’t have records after the calamities of people living longer lifespans, nor is their any indication that people are getting noticeably better at wielding magicks. When Yoshi P said that Emet and Hyth when reborn would just be a little better at things than everyone else, the implication seemed clear. The soul is Unsundered yet the body wouldnt be anything special. Combine that with Emets line about being stifled by his flesh (which he took from a random citizen of the 1st), the fact Ardbert was able to hold his own against us despite us being 7 times Rejoined, the Ascians and their “uplifting,” all the comments on our weak aether in Elpis and Amaurot etc. etc.
Yeah, this one tracks for me; even if a fully unsundered soul is in a body on the Source, they're still in a body that's a fundamentally different species with different abilities, so they can't make full use of what the Ancients could. They'd also be being raised and learning how to manipulate aether in a world that's largely used to far smaller aether reserves. As comparison, imagine if random cars suddenly had nigh-infinite fuel; theoretically it's possible to make a car that can use that for amazing feats, but realistically you're gonna end up watching the same old Toyotas you always see doing basically the same stuff Toyotas always do, they're just worrying less about where the nearest gas station is.