How did you come to that opinion?Also also, despite being 1000, Frieren is apparently still considered young.
I'm sure we'll see Kraft again. He's apparently a big shot, going by their dialogue. At the very least, he's accomplished.
edit: I see it's when he calls Frieren young, because he finds her lack of belief in a Goddess to be a thought suited to the young, while he's supposedly lived to much that everyone who knew of his deeds has died and only the Goddess will remember who he truly is.
But that's just because Frieren only defeated the Demon Lord 80 years ago and people still remember her. If she had defeated the Demon Lord in the first half of her life and isn't as emotionally stunted as she is, she could feel similarly about how no one remembers her deeds from 500 years ago.
After that comment, he actually invited Frieren to share her life story with him and he'd do the same back, then he'd praise her. She declined though. So I don't think he's necessarily aware of her true age.