Does anyone else notice that "good days" seemed to be immediately followed by "bad days"?

My husband, who is in his late 70's has early to moderate dementia of an unspecified type...most probably Alzheimer's. He is on both Aricept and Namenda. They seem to have slowed the progression of the disease slightly from when he was first diagnosed. Maybe...anyway. I have noticed the last six months or so, he will have two or three very good days when I can hardly tell he has dementia. He may ask me the same questions repeatedly, but his cognitive function seems almost normal. This will always be followed by one or two really bad days. Yesterday was the best day he has had in over a year. Not only was his memory functioning well, but his personality was much more like his "old self." Today, he is totally lost. He is more confused that he has been in a year. He is obsessing over misplacing a shoe horn. (I am at work, one block from my house. He is home alone) He has called me four times in the last one and a half hours, and can't even remember that he's already called and that I have explained to him that I will be home soon and find the shoe horn. He walked down to my office, to bring me the lunch that I had packed for him and left in the refrigerator which is something he never does, and sat in my office and obsessed some more over the shoe horn. Has anyone else noticed their loved one having really good days always followed by really bad ones?