Ultimately this depends on how long you expect bitcoin to continue its remarkable exponential rise against fiat.
It should be pretty obvious that if, for example, it goes up 500% every four years, you can just borrow against it (half the value, 8% interest, as on Coinbase), and take out a new, bigger loan every few years, while still increasing your overall net worth.
However, it should also be obvious that nothing goes up at that rate indefinitely.