@Owyn, she might read a lot, but she has a terrible memory of what she reads(revealed way later) (this means very little to the story, as it doesnt help her get books faster anyway(at least for electricity)).
just as an example, I hardly remember anything about biology, social Studies or...
isnt there an animal that can live like forever, its just that it dies because of it shell or something?
Since Rimuru has skills like wise something-something, and other similar skill, cant they control his DNA splicing, making sure they don't degrade or mutate in a negative manner?
Or at least...
that happens quite often with webtoons, where the artist is still ... "evolving", starting collabs with other artists
or the other way, they start out way too ambitious and later learn a more time effective way to draw, collabs ending, etc etc