In fact, we realized all guilds are basically temporary arrangements of diverse people for certain purposes; they grow, change, and dissolve even as the people in them grow and adapt to new situations. A lot of people become upset by guild changes, especially if they're trying to lead and lots of drama ensues. They know in their head of course that no guild will last forever, that WoW itself will not last forever, but they still become sad when, eventually, things fall apart.
My friends and I are discovering that there's no need for this sadness. A great guild, you could say, is like a Buddhist Mandala: an impermanent gathering of individual grains of sand, destined to live its time and then get brushed away. Most of my friends come from a guild that had served us well and gotten old with us, and leaving it behind just felt like the right thing to do. Someday our new guild will get old and we'll leave it behind to do other things -- and that's okay. The purpose of a guild is not to reign eternal, just to let us do what we want to do together now, and enjoy every minute of the present.