making Bitcoin as a very long-term asset is a risky thing and I think it's an unwise act because Bitcoin is unstable and also it wont be in its glory forever because its not impossible for something better will replace its position in future. remember when some countries forbid the use of Bitcoin. it possible many countries will release their own digital currency. Youd better prepare your next investment plan before Bitcoin falls and vanish.
For this reason it's a good idea to split your money among some different investments, but don't forget to invest into Bitcoins too. I believe most people here will have to wait a long time yet to retire themselves and until this time comes many events can happen that will affect Bitcoin's price. Not only Bitcoin's price, but our societies, economies, etc... I believe the best to do is to build our own way without trusting our future on the country's pension, in some countries like mine it's already going bad, very unstable...