To retire comfortable, honestly, I would say 1,000BTC.
1000
BTC is enough even for now, 5% withdrawal rate give you 30k yearly expense. 5% yearly appreciation rate for Bitcoin is very conservative. In 5-6 years, I think we only need 100
BTC.
Implying a 6k USD BTC price, which seems incredibly low in 5 years' time. In one year's time, I could see that, after a single bubble crash. I think 2 more bubbles in 5 years is a minimum, with a 15k BTC being the least result which can be reasonably envisioned, so 30 BTC should do the trick, if you don't need to travel, and your medicall is socialized. 4 bubbles is more likely, so 10 BTC is probably going to be adequate to that scenario.