Martha, I hear you. I guess we just don't know the answer. Do you feel any different cognitively when in ketosis?
Stavia, I don't know that I do. I am treating it as pure prevention, based on what the doctor at the conference had to say about compromised glucose metabolism in the brain and the benefit of keeping neurons nourished periodically with ketones. It might turn out to be of no real benefit, but there are enough big guns interested in it to make me think it's worth a try. And it does keep me from adding body fat (sometimes a little too well).
I have pretty much lost interest in very-low-carb diets, though. I never did go much lower than 30 g for very long. It's easier (and maybe just "better"?) to get there by fasting. At least it is for me. I even made cookies (not very sweet, but definitely cookies) last week, ate them, and zoomed on into ketosis a couple days later, no problem.
I should actually probably share that recipe. It's sort of a nut-butter/oat flour/maple syrup template for something that satisfies the need for a treat without just killing you with sugar and flour.