Implications of the continuity of Currier "languages"

[Koen G]

Could they be like scribal habits that changed as the project went along? This still leaves open both the possibilities of one scribe evolving or one or more others jumping in.

I can imagine a scenario where first you don't abbreviate much, then you start abbreviating in some situations and then a lot. I'm not saying that it must be abbreviation, but this is an example of a gradual process I can think of, which would tend to vary based on the habits the scribe employs while writing a whole segment.

But in concrete terms, what is it exactly that causes this gradual change? Vocabulary? Or the increasing and declining use of glyphs/clusters in specific positions (kind of like morphemes)?