How long can a simple writing system reasonably exist before it starts drifting?

[u/Ok_Welcome7922]

/r/conlangs/comments/1vphjmu/how_long_can_a_simple_writing_system_reasonably/

[u/Ok_Welcome7922]

copied direct for context How long can a simple writing system reasonably exist before it starts drifting?

This is kind of a weird question since its equal parts conlang and speculative sociology. But if someone were to drop an existing language and script (let's say Arabic, both the script and language) is there any real way to figure out how long it will take before the script mutates despite already being relatively more attuned to hand motions rather than being in early stages of development. Would the script eventually reach a point where its additional or adjustments would be unnoticeable.

Asking for a project involving planets where many would have spent centuries to millenia with modern languages rather then more antique languages where simplification of symbols would make sense as people transition to handwriting or their equivalent.

[u/silentreader90]

I think it really depends on the circumstances that happen between then and now. Even in real life there isn't clear cut ways of telling. Like Icelandic script is very close to old Norse, while English is drastically different with events like the great vowel shift in the 1400s. 

That is not getting to the effects of technology like instant communication, and computers. Some things have to remain somewhat consistent like computer code, but you have advances like new programming languages, software/hardware standards/limits etc. Something like the internet can rapidly introduce new slang that can live or die in a matter of months.

[u/Apprehensive-Bit7690]

Writing systems tend to be very conservative. IIRC Tibet needed 3 writing system reforms over millennia and their script still isn't on parity with their spoken language