Busy life or fickle friendship?

Friendship is a funny thing. For as much value as we place on it, sometimes above family relationships, friendships sometimes feel fickle. Not that the "friend" is necessarily a fickle person, but the give and take of friendship seems to be fickle, inconsistent, and out of whack with my expectations.
How often do you try to schedule a lunch or coffee after someone suggests it, and then he or she  can't make it work? Schedules and plans shift around as we go through our weeks, and those iffy plans made with a friend get pushed aside.
Someone says, "Hey, we need to get together sometime."  I never know the protocol. Am I suppose to initiate that or do I assume they will contact me to make a plan? {Sigh}
My husband is often good at remembering to follow up on these conversations. I have been frustrated many times when I've tried to set up a time to meet a friend. Sometimes I get so frustrated I quit.
No one likes to be harassed either.  No one wants to be guilted into friendship, and it doesn't work either!
Everybody has acquired friends and acquaintances from various stages of life--childhood, high school college, work, parenthood, children's schooling, or other activities.
Who will you count as friends years from now? Many of these friends we see in passing. At one time there may have been deep connections with them, but now life circumstances (we like to call it "busyness") get in the way. Some friends I am reunited with in new social situations; others I have to work at with them to get together once a year (its worth it!); and often I feel left out of others' lives that I was a part of at one time. It's a fickle thing, friendships, bedeviled by time, work and family commitments, volunteer activities, and life in general. For the unnaturally outgoing or well-spoken person, as I am, initiating is a personal challenge.
Its difficult to remember my last good phone conversation with a friend especially with so many other ways to connect with people. Now more often than not I exchange a text rather than talk on the phone or in person. Its good, but still not quite as good as having a conversation in person. And yet, I'm to blame, too, because at the end of my day I just want to curl up at home. So, is life fickle, are my friends fickle, or am I fickle? Or is it just a stage?
What must each of us give up in order to invest in friendships?