Friendly reminder that Klaus’ letter was preceded by “that is the beginning of another story”, which is meant to highlight key components in the letter, such as Klaus wanting to thank Caroline in person. This suggests that they do eventually meet up, and that their meeting is not a mere fleeting chapter in their lives.
This isn’t a nod to their friendship. They’ve never been just friends. This is a promise of a romantic future.
There is no doubt in my mind that if Caroline and Klaus were to ever reunite (and according to the finale they do) that Klaus would want something romantic from her. And if you believe otherwise, you’re kidding yourself.
However long it takes is a throwback to a romantic scene. A romantic scene that suggests a promise of a romantic future between the characters. This isn’t mere banter between friends. Because Caroline has never been just a friend to Klaus. It’s a promise of a romantic future.
“that is the beginning of another story”
“however long it takes”
Eventually this story will be realized. And it isn’t a story about friendship.