With current inflation rates you will never have enough money for retirements. I guess that you need at least 20 btc to play if safe
Well, there is no ceiling in that sense, the more BTC the amount is, the better in this idea of taking it as a withdrawal liability, the issue is, how much do you need to have to have a worthy withdrawal, it is not a question of 1000BTC or 1BTC to a worthy withdrawal , so in reality it is something (very) individual. Then, in any case a retirement fund based on several assets is always better, so within that 100% of the money that you stipulate, bitcoin should never be 100%.
I agree with you and Bitcoin should be used as one of the options not the only option as a place to save money for retirement or old age, however risk and money management needs to exist, we cannot be fanatical in life, what if the seed phrase disappears and other things that interfere with your bitcoin, maybe someday if you can't withdraw it it becomes a problem and you only have assets only in bitcoin, that's too dangerous when viewed from the risk of bad possibilities, we should have other options such as land, gardens, gold or anything that might provide value to us in old times, and I think it is much better for financial health, where we have bitcoin and other assets besides bitcoin.