When I first started fighting the LBD I figured like everyone else that if I spent the rest of my MCI time constantly pushing myself, in the way you would push unused muscles, I would somehow last longer, remain "Me" longer. The problem is, after a year to 18 months of this I realized almost every time I had a plateau which resulted in a permanent reduction in cognitive ability it was immediately preceded by me or circumstances pushing me beyond my capabilities. I just got worse, not better and if this somehow slowed things, it is not obvious to this observer.
So to test this I purposely toned that crap down, not stressing myself as much as possible, not letting myself get into situation that would be overwhelming and so on. You know what? I felt better and have enjoyed this time WAY more than when I was being "good" and over-doing it all the time, simply "because."
When you think about it, asking a dementia patient to keep pushing things in order to somehow make their time last longer/be better, etc, is as stupid as continually trying to race a car with no wheels.