I don't think there is an answer to that question. My Mum went downhill quite quickly but then she was in her late 80's on the other hand my wife has got worse over the last 5 years but (she was diagnosed at 55) at nothing like the rate my mother did.
People's experiences will differ be wildly that I doubt you'll get anything much out of it, some become aggressive some become more passive, some become introvert some (embarrassingly sometimes) more extrovert. Although there are a lot of things in common each is an individual journey.
Sorry I can't be more helpful.
K