i think is Bitcoin is safe in my opinion as compare to paper money because no one is stolen your money, you can purchase goods in safe mode
If keeping it safe from being seen by anyone, it is safe, but how long? we never know, bitcoin price moves very fast. I think it should be half fiat and half bitcoin if he want to keep, who knows what the price of bitcoin maybe. and might fall, so its better to be wife, put half in wallet and half in fiat.
because bitcoin is very volatile. you should be ready with all the possibilities that exist, including losses
1 BTC could be down cost only $ 100, it may be due to fluctuations
so you should know the risks