The aging Batman thing is starting to give me second thoughts. I think Affleck's casting was the result of a confluence of factors: Warner Bros. wanting a big star as Batman, hoping to secure Affleck long-term with the studio, and of course, Zack Snyder's obsession with The Dark Knight Returns. But it's starting to seem like casting an older actor as Batman might not have been such a good idea in the long term.
On the one hand, I think it makes a lot of sense to have Batman be older and wiser than the rest of the Justice League. It gives him an advantage over the others and further explains why this normal human being (even "peak-level") can stand toe-to-toe with a bunch of superpowered metahumans. Batman has typically been depicted as the main tactician of the Justice League, and having him be a veteran, battle-hardened crimefighter only improves that ability.
On the other hand, how old can Batman get before it starts to affect his ability to physically fight? I get that this is fiction and you can get away with a lot through stuntmen, etc. But this isn't like Robert Downey Jr. as Iron Man, who wears high-tech suits of armour that protect him and allow him to efficiently target his foes. With Batman, we have to assume that this guy is still in peak physical shape and a world-class fighter. With an older actor, suspension of disbelief gets more difficult, even though Affleck was roughly the same age when he was cast as Bruce as Downey was when he was cast as Tony Stark.
Ultimately, I'm rooting for Affleck because he's probably my favourite actor yet to portray Bruce Wayne/Batman in live action. But I'm not sure how many movies he has left in him. And I'm worried by how much his physical appearance has deteriorated recently. At the time of the BvS premiere I was struck by how healthy and fit he looked (especially since he had had that weird Botox look only a few months before). But I wonder if going through a divorce has had some negative effects on his health and appearance. There are signs he's started drinking again. Sometimes his face looks weird because of apparent Botox treatments, and then other times he looks puffy and just plain old.
I get that Snyder likes the image of a "crusty old Batman beating up bad guys", but I also don't think we want a late-era Roger Moore as James Bond equivalent. It's a fine line to walk between having an older, mature Batman, but also one who looks physically capable enough to still be that fearsome avenger who can kick anybody's ass. And regardless of the character's appearance on film, I hope Ben looks after himself just for the sake of his own health.
