Anyone here familiar with ALS?

I know it is a fast moving, debilitating disease. I was wondering if someone had an idea as to how long a person could live at home once the limbs quit working properly and standing up by oneself became almost impossible?
Also, is it common for someone to be functional one day and almost completely unable to work their legs and one arm the next?
Does it come and go? That is, do you have bad days and worse days or does it stay worse once it reaches that point?

I was asked to assist in some home modifications for this person and when we went to assess the situation the home health nurse took me aside and told me that she did not think that the lady would be at her son’s home long enough to make use of any bathroom modifications we could do because she would lose the ability to get into the power chair, or even operate it, within a short time.