I should have followed that discussion on souls more closely, but alas RL got in the way. Now, to be super duper honest, I've gotta say the whole soul fraying concept isn't my cup of tea. I mean, adding such hard mechanics to a somewhat abstract idea kind of diminishes its' value, and sets a handicap for most beings, while also setting some tedious existential questions. I mean, with the Lich example, the Lich's soul would end up being a completely different one, or an amalgamation of sorts. Though it's a cool concept, that could produce some wacky creature ideas, I fear it could, in the long run, be sort of limiting for worldbuilding purposes, new ideas that could emerge and whatnot. Also, though it's not my place to judge, it is my personal opinion that the Sky of Pyres would have far more cosmological weight, and could produce interesting dilemmas and ontological queries if souls were eternal, but limited by nature. 

 Also, don't turn my spoopy ghosts to dust pls.

 In all seriousness, and if I could myself propose something, I would say that it would be better for souls to remain nebulous, ill-defined and ageless cores of being, but very much finite.