Gotcha! Sorry about that!
(I've just seen that 40 year stuff bandied about so much as some sort of proof, that I reacted to it without reading thoroughly).
The relevance of the 40 years isn't that the memories might be flawed (although that could go either way), but that through multiple political campaigns and over 4 decades this hasn't been brought up.
While certainly odd, I do not see it as proof either way.
Memories that old are a funny thing. Some are crisp and clear, usually because a great deal of adrenaline was involved. I have some like that, and there are other, more mundane events I have little recollection of. Some things just don't stand out. But I have heard people relate events from our mutual past to me and the accounts are not the same as my recollections (even if they placed me in a better light than my own recollection of events).
So, even individual memories are not completely reliable in all cases, any more than eyewitness testimony, those memories can be altered from initial perception, being re-remembered/retold in slightly different iterations, even discussion with others which might cause a story to be remembered in an embellished form or to depart from fact. Even the recollection of participants involved can change over time, as a friend had placed me at several events in decades past which I know I had not been present at. The more people who independently recall a specific event or person, the more likely that is to be correct or close to being correct, provided they haven't discussed that among themselves, in which discussion stories (and the memory of them) tend to blend.