Holding them is a good way to make profits in future but some of them should be invested in trading to multiply bitcoins in a quick them along with making regular profits but if you don't want to take any risk then best choice to simply keep them safe in wallet and sell when price goes higher.
You can not keep all the assets in Bitcoins. it is very risky. It is best to part of the assets to invest in other projects
The future of bitcoin is unpredictable so if you are investing all your money in bitcoins then it can be very risky as you never know what future will show us so the best thing is to diversify your investments so that even if one investment fails the other can take care of your money.