Snapchat can’t die because it won’t grow old. Or more to the point, apps and services based on ephemerality will have greater longevity because there is no content to age, grow tired, lose fashion or become embarrassing.
Snapchat has more in common with how we actually live every day. Despite technologists best efforts to persuade us otherwise we still don’t record every conversation, every moment of our lives. We still rely on our wonderfully unreliable memories to recall (or not) the things we may or may not have said or seen. This is the human experience and Snapchat feels like it is more attuned to how we are than Twitter, Facebook, YouTube or Periscope.