I came up with these concepts in 6th grade during a “Luminary Lock-in” (A “Luminary Lock-in” was an overnight retreat where kids would make those wonderful lights outside of church on Christmas Eve. You know, those things made of a gallon milk jug, sand, and a candle”).
Convenience-Based Relationships Theory:
These are relationships you have with the kind of people that come and go in your life. The kind of people with whom you might have gone to school or worked for a while, or the guys at poker night. These kinds of relationships are formed on the basis that you have something in common…at the time. These relationships are based on how convenient it is to have them. When you graduate, move, or switch jobs, these are those that don’t always persist without a lot of work to keep up. It’s hard to catch up – except maybe nowadays on Facebook – and quite honestly, you don’t really care. There’s nothing wrong with these, nor is there a moral judgment of any kind here. It’s just a matter of fact. These are the people who traveled on the road with you for a little while during the portion of the journey you happened to share.
“Bookmark Friends” Theory:
Now these…are those friends – and on average, you will have very few of them, because it’s a question of quality here, not quantity – that you meet up with that when you do, you skip the “Hey, how’ve you been…blah-di-blah-blah” act. These are those friends that you trust have been well, with or without you, and think likewise of you. They are the ones that you chat with every now and then, but when you do, not a day has gone by since you last did. These very special people in your life are the ones that can live far away from you geographically, but you keep very close to you always – and without even trying. Bookmark friends are those ones that, no matter where you are in your life, no matter how long it’s been, and no matter what physical distance separates you, you can always pick up right where you left off – just like an old book you dog-eared. These are your closest people…the ones you walk through Hell with, the ones you meet in Heaven.
“Single-Serving Friends” Theory:
(Please see Fight Club).
#bookmarkfriends
In Between Degrees 
Well said.
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[…] Think of two friends, walking along the road, sharing their story together for a time. At some point, they come to a fork in the road and grow apart. This does not necessarily mean their friendship did not have lasting value, but that they simply took different paths in each of their own lives. This does not mean their time together was meaningless because it was not shared forever but very much the opposite. Each of their lives were enriched by each other for the time they shared their journey on the same road together. Perhaps, they’d meet again one day when they might share another part of the road together once again. More still, the roads on which each of the friends is traveling may even be parallel and intersect on many occasions. […]
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