Really? Would you vote for a 90 year old for POTUS assuming they were in excellent health?Not a very good argument. We were talking about whether a 90+ year old man can have coherent thoughts and conversations. That's a lot different than whether I would vote for him for president. Good try though.
"Almost all elderly people experience a cognitive decline the symptoms of which are difficult to distinguish from the earliest manifestations of dementia; yet in most the condition does not progress to dementia. It is possible.....that anyone who lived long enough would become demented; but most people die before then." Richard A. Posner 1995 University of Chicago
Would you not agree that 90 years is kind of "getting up there"?