"Tell me if you've heard this before ..." If someone asks this question before lamming in to a story, it's quite likely that you have, indeed, heard the story before.
"But did I tell you the one about ...?" You might not have heard this one. Keep an open ear.
We have a code in our family: if we've heard the story a handful of times before, we hold up the number of fingers for the number of times we've heard the tale.
"What about this one? Have I told you this?" Blah, blah, blah, yadda-yadda, yeah-yeah-yeah. Yep. Yup. Heard that one.
So what else is new?