This is good view to hold your bitcoins with your earnings. Try to invest your bitcoins as like how you hold the stock or gold or something precious. However I am just holding the bitcoin from the earnings from my signature.
It is very risky if you are going to invest all of your money (cash) into bitcoins. Because of its unstable pricing then nobody really can't tell if the time you are going to buy bitcoins will tend to give you profit or not. That is a good way on how you are going to put your money, just a portion and percentage of your total assets is a good way to invest in bicoins.
For me the risk is really low. But I can't survive with only Bitcoins currency. All shops and stores I need to buy things on my daily life don't accept crypto-currencies, so I need my local currency also. A good investiment on Bitcoins would be the month savings. maybe 10%-25% of our money into Bitcoins can help to make a good profit on medium-long term.