Lost my Dad in 2014. WW2 veteran big unit of a brickie, was an intelligent, funny, good natured fellah.
Although his slide was mercifully shortened by the way he passed, he was deffo losing touch. Couldn't always remember his grandkids names, would repeat a story he told you 5 minutes before, and was generally not really 'present' and getting worse.
But...to your point about long term lucidity, he could recollect and tell things from growing up in Liverpool in the 20's and 30's, and do so with clarity - but, as you say, was much less able to
recall things from earlier in the day, or week, or recently.
Sorry you're going through this, and no need to apologize for it - you've brought some conversation to the subject, and some memories from other posters.