Re: How many bitcoins do I need to retire in 20 years?

I would estimate 10-20 BTC

Seems very low to me. Not sure from which country you are from but I would assume you need at least 1-2btc a month at current prices to cover all living expenses, pay taxes, enjoy leisure, etc. You would need these 10-20 per year just to live.
Of course the bitcoin price will rise and you will need less coins,but the living expenses are rising alsim

It depends on the bitcoin price. I reckon the bitcoin price will double every two years, so that price will be $500,000 each then.

I don't think that is possible, we don't know whether bitcoin will exist that long or not and even if it survives its very difficult to touch that price.

Even on $4000 seems unrealistic and its hard for bitcoin to reach that price soon. How much more in $500k then its very very imposible to happen. As other said we wouldnt even know if bitcoin would last to for so long that it could rich some moon amount.

I used to think the bitcoin price will double every year for the next 20 years, but with the current slow development, it seems very unlikely.

you never know when will price comes up or double
it can be every 2-3 years in 20 years expect even five digits price