Indeed, Bitcoin is always relevant to invest. Because it always grows. You always develop. The only thing you need is to have nerves of iron and patience for you to wait for these years and turning points in his life.
I can not say that the price of Bitcoin is constantly growing. Bitcoin is very volatile, its price rises very high, then falls very low. In this case, you can still make extra money on such changes in the price of Bitcoin, selling this coin in time and buying it on time.