In earnest we often feel loyalty isn't affected by by anything, but that isn't true time and space affects the onus of friendship and even the most closest of friendship as well. In so many instances changes and circumstances makes people rethink their loyalty towards you. Sometimes it might not be your fault but sometimes people get reorientated as a result of growing up and embracing other endeavors.
However the truth is that Friendship should stand the test of time but not everyone is built for a long term Friendship, don't blame them, some people have a more stronger mentality others don't and we can't fault people for this frailty. In essence people choosing to be permanent or ephemeral isn't as a result of their Inability it's as a result of the way they were built. If you're lucky to have a friend who understands the essence of longevity then we're lucky and not deserved.