The late . . .

For how long following someone’s death do we describe them as “the late”? I thought it meant the recently deceased, yet I still hear people refer to the “Late John F. Kennedy” and the “late Marilyn Monroe.” But I’ve never heard “the late George Washington.” So where’s the cut-off between late and just-plain dead?

I assume that if a person has been dead so long that no one living at the present time was living when that person was alive then that person is “just plain dead.”

‘Hurry up, Mr. Dent or you’ll be late.’
‘What’s the rush?’
‘I mean you’ll be the late Mr. Dent. It’s a threat, you see. I’ve never been very good at them. Although I did win an award for my fjords…’

Hitchhikers Guide to the Galaxy, Douglas Adams.