Try memorizing Desolation Row
The crazy thing about Bob...well, one of 'em
... is that he may be the only classic-era performer still working who has never used a teleprompter.
He talks about this at some length in his faux-tobiography Chronicles (I'm not sure how aware Bob is of what he got wrong, and I don't know that it matters
-- still a delightful book that I've read a few times), when he read a translation of The Odyssey one time while recuperating at a friend's house in NYC, and startled when he found that he could recite back a good bit of what he'd read without having even tried to memorize it. It just happened.
So he thought to himself, "Well, instead of writing short pop-folk songs that anyone can sing, what would happen if I wrote long, complicated things that were more like Homer than Woody Guthrie? Away from plain language into epic poetry?" I'm paraphrasing, but you know the rest.
Nowadays, he's mostly sticking to the same setlist for a variety of reasons, but it's not like he's singing mostly short or easy songs.
The decade of his that I saw him most often was during his 60s (not THE 60s, but rather the Aughts), where he was famously performing 100+ shows per year, with not a single setlist repeated. I saw him on a 3-night run in Boston where he played 48 different songs, repeated only two of them, twice each, so not a single song played all 3 nights. It was like a magic trick!
I saw a goodly number of performances of Desolation Row, Visions of Johanna, It's All Right Ma, Like A Rolling Stone (an "easy" 7-minute jaunt, don't forget!), Gates of Eden, Chimes of Freedom, and others that any normal person would have difficulty singing one of, and watched him do them all, and more, again and again... in his 60s! Easily 200 different songs with my own two eyes, and probably more.
I was also just reading McCartney's explanation of why and how he uses a teleprompter, and it's mostly during Beatles songs!!! He'd found himself slipping into autopilot, and it was too easy to get distracted. So yeah, now he
reads Eleanor Rigby (the example he gave in this interview) to make sure he gets every word, stays in the moment, and doesn't get ahead of himself.
It's kind of the flip side of memorizing -- it comes easily to him, but he never wants to take the
performance for granted. For somebody there that night, it'll be the only time they see him, and him messing up something simple in their favorite Beatles song will not make for a charming anecdote. Get it right! So he does.