Well,I think it really based on the person who using bitcoins.If someone considering bitcoin as an investment not a means of currncy then he have to sell it when the goal price of him reached.
If someone thinks bitcoin as a future form of currency then he need to hold it forever because crypto currency is going to be the future currency.
Yes it true that there are people who are piling up bitcoins to use them simply as currency of the future. At the same time, holding many coins will give the advantage of selling at right time. This in itself is an investment. But many do not trade their coins for a brighter future and higher value. Today the market is volatile and we are able to find a drastic fluctuation in the value in a very short period of time. But in the long run some of this investment can really fulfill the need of the hour coming up then.
People who may use it as a currency and simply are stacking up their bitcoins have actually earned them through trading etc. One who has put in money may little consider the value of bitcoin as a currency compared to it being an investment. It is also important to fulfill the purpose of any investment to utilizing it in the best way possible. As the saying goes, the one who knows to spend is the one who knows to save.