The main reason why we should buy now bitcoins is for our own investing. It is really effective that you buy a bitcoin now and invest it in your wallet and wait many year and see the difference.
This is pathetic idea, investing is not for saving long time/years (like what you said) to test that this is effective. This is for securing the future that actually earns a profit, but this is no assurance, it is possible to lose or success. Im just pointing out that holding bitcoin for the long period of time may cause bankrupt of the user. Or else if bitcoin become success in future they will have lot of money if we hold and buy bitcoin at this time. The price decrease and actually increased in the other day, as we see (the bitcoin trading) price dump and recover in just a day, this will the reason why this crypto-currency success in the future.