I think first we have to define "long term".
Personally, and I know this may not be that popular on this forum but I don't see Bitcoin proving its value (long term) for some time because we have not see enough attacks, or real life events unfold. For example what if one of these global cyber events happens and it renders many peoples Bitcoin investments for a long period of time. Its just a thought.

Short term Bitcoin has proven itself.

I dunno, guess we have to wait and see.