If friends disappoint you over and over, that's in large part your own fault. Once someone has shown a tendency to be self-centered, you need to recognize that and take care of yourself; people aren't going to change simply because you want them to.
Statesman, yet friend to truth! of soul sincere, In action faithful, and in honour clear; Who broke no promise, serv'd no private end, Who gain'd no title, and who lost no friend.
He who has achieved this state Is unconcerned with friends and enemies, With good and harm, with honor and disgrace. This therefore is the highest state of man.
What I know for sure is that if you can survive 11 days in cramped quarters with a friend and come out laughing, your friendship is the real deal. I know ours is.