Best Friends For Life And Eternity like BFFL, but for ETERNITY, as in AFTER life. AS if you and that person would find each other after you both died, and that you would alwaysstay friends.
You are at your friend's house and are having so much fun! She says: You are my BFFLAE!
You: what is that?
Her: Best Friend For Life And Eternity!
You: Totally!
Her: See you at school tomorrow!
BEST FRIEND FOR LIFE TILL DEATH DO US PART; used by many teenage folk to express how much they love their best friends and how close they are with each other. The day they aren't best friends anymore, is the day they die. Self Explanitory.