i don't really think using bitcoin as a retirement account is the best option because the future of bitcoin is not certain as nobody really the future. Predictions is possible but it is not 100%. It could be profitable at the longrun or not profitable at all. Well, everything has risk, you just have to gauge the risk very well before taking the decision.
If you hold 60 to 70 BTC then I believe it is enough for you at the time of retirement. You don't need to hold anything else or you don't need to invest anywhere else and this would give you the best return on investments in the future just wait for next 5 to 6 years and you will be the wealthy man.