You can hold, but I suggest that you don't hold the full amount in BTC.
You can consider to use part of the fund to buy some very popular alt coins, such as LTC or DOGE, when their prices are low.
So you will be able to migrate some risks, and not solely be affected by BTC price fluctuations.
Or he can invest his 12btc in ICO project, usualy some altcoins are get famouse then the price is rise until more than 250% when the coin get in the exchange site.