Pity Professor Taleb is not about to offer his thoughts on the claims of guaranteed forever.
As a practical matter I have long term investments (distinct from my trading portfolio) in what I believe are low risk investments. But I am well aware that nothing, absolutely nothing, in this world is risk free.
As a perverse example, on 10 September, 2001, I would have wagered all that I own that the World Trade Center would be standing at sundown the next day. Apologies to anyone offended by my use of such a notorious example.
If you live long enough, you know you have not seen everything, and you know that there will be events in the future that are beyond your dreams of today.
Another example, my grandfather was born into a wealthy and privileged family in the 1800's, (think Downton Abbey). As a person of wealth there was a horse drawn carriage with a driver for his use, that was state of the art. Within his lifetime he saw the creation of cars, aircraft, telephones, satellites, two world wars (the first of which, the so-called war to end all wars, left him crippled for life), nuclear weapons unleashed on humans, and a human walking on the surface of the moon.
You do the best you can with the risk you know of, but the outliers will occur in time. It is when the things of which you are absolutely certain, turn out to be wrong, then you have problems.
Not to be too maudlin, and I certainly do not advocate converting all your assets into canned foods, in preparation for the apocalypse, but I do think about the impossible actually happening, and what do I need to do now to minimize the impact of the event.
Good grief that was a long winded bit reminiscing. Who let grandpa lose on the interwebs again? Keep him in his room.
For the bitcoin advocates (I have nothing to do with them), what will be the impact of quantum computing on their value? Present day encryption will have the security of a post-card in a world of quantum computing. Will a resurgence of mining lower their value? And finally, as always, there is the government. They can mess about your greatest plans in a twinkle.