What an interesting question. I guess for me, if I can connect with the main character, believability falls in line. Like you, I would have had a hard time connecting with (and therefore believing) in the scenario you described, of people holding on to something for 20 years. I guess I can believe that, but it sure doesn't resonate with me. And I disagree with another commenter here who said that annoying characters do not a bad book make. I won't read a book if the characters are annoying. I guess that doesn't mean it's BAD, but it does mean I'm not consuming it.