It's not a journey any one of us would chose but when present with the challenge we rise to the occasion!
With Mom, who has Alzheimer's it does seem to come in spurts... with ebbs and flows. I see Mom at least three times a week if not more. Like you MIL, my Mom started falling occasionally. Most were in the late afternoon or evening when she was tired. I blamed it on the time of day, or anything else I could think of. But when I took off the rose colored blinders I realized she was also having trouble getting up from a seated position. She is walking slower. She is shuffling more. Then there was the leaning to one side when she was walking. Yep the disease is taking little bites. Those little bites do seem to come and go for a while. She will have good days and not so good days. But when you look at it over time you see the digressing. Yep, the falls seem to herald the start of loss of ambulation.
Not all Alzheimer's patients have the same rate of progression and they do not lose the same things at the same time. Mom lost her ability to communicate effectively rather early... yet she has maintained her ability to ambulate long after the ability to communicate. There are a number of residents in Mom's unit that are in wheel chairs but can still communicate effectively. They can seem to stabilize for a while and then take a dramatic turn for the worse. Mom took a dive in cognitive ability two years ago then seemed to stabilize. In the last few months I have seen a dramatic decline.
My Dad has Vascular Dementia and it had a very different pattern of symptoms vs Alzheimer's. He was diagnosed in the late 1998's and lived until March 2010. Over those 12 years he was rather stable for most of them. Short term memory loss but retained reasoning, reading, understanding and the ability to manipulate numbers. He did have many more delusions. The last 6 months were a very rapid decline with delusions, falls, excessive sleeping, and a rapid loss of abilities. This related to A-fit and other vascular events. Mom in her Alzheimer's lost her ability to reason, understand, read, and manipulate numbers quickly.... along with the memory loss. Dad was continent even after Mom became incontinent. So it's impossible to compare the two.
You never know about the progression. A couple of months ago I would not have given Mom much time. But now, she's holding her own. Who knows what tomorrow will bring
That's just the way it is.