[Say, it isn't that bad!]

Originally Posted by Andreas

Perhaps immortals like those in Highlander should have some memory related advantage since they can remember things from very long ago well. The maximum memory capacity of the human brain also doesn't seem to be much of an issue for them (though I'm not sure how long it would take for that to matter).

Perhaps a version of Photographic Memory limited to only preserving memories at least a hundred years old (that way memory on human time scales would be the same) and perhaps also skill degradation if those rules are used.

I don't know whether it's relevant to the OP's campaign, but the only immortal in Highlander: The Series to have forgotten things is Methos. Who's at least 5,000 years old.