I would say don’t all-in since Bitcoin still contain high risk due to its volatility considering that we are talking about retirement money which you will badly need in the future. You can’t afford to hold longer if you are already retired while the price of Bitcoin that time is lower than your average buy. There’s a lot of time which Bitcoin plunge huge percentage of the price that makes it still a high risk.

I think splitting your retirement plan to stock market, cash in the bank and Bitcoin will be a good idea since you can hedge the risk if one the 3 market crash.