I would sell them all at once and the then quit with Bitcoin because I can already make much money with it and I have no time o wait for the future.
It is not even if the future is going to give us want we want so I am not taking the risk then.
Yeah 500 btc is a really huge amount to hold so I would prefer to sell half of them and convert it to fiat currency and invest that money in real life business and rest will hold for the future.