I like your approach with the 20 minute intervals. My wife has MCI and not as severe as full on Alzheimer’s or dementia. However, the emotional comport is similar. My thinking is now this; I need to manage my exposure time carefully. There are times when I need to just exit the situation for a time, and also plan for days away regularly or even a week away for a couple times a year.
I just cannot devote my entire life to my wife’s interest alone. I believe my calling is to serve others and love them too, and if all of my time is consumed with my wife alone, I’m unable to do that .