That's the thing with Alzheimer's. It affects everyone differently. Where in the brain the deterioration happens determines which skills you retain the longest (or lose first). How fast it progresses in very individualized too.
I have observed nearly 60 patients at my fathers facility and have seen over 25 of them come in and pass away in the past 4 years. Only a few where there when my father arrived. He's one of the last still there from back then. Average life expectancy is around 10 years from diagnosis but that's increasing now. Not because treatments are better, but because they are detecting it earlier.
The number one protection against it is to keep your brain constantly challenged and growing so that you have a greater depth of cognitive complexity built up to survive the onslaught of the disease. The deeper and stronger your brain is wired, the more logically and mentally disciplined you are, the better your chances of holding it off longer.
In other words, scatterbrained people living in the moment go down hard and fast when ALZ comes to get them.