When it comes on being rich then there's no such thing about unlimited fund or Bitcoin on which we would really be always wanted to have that even more.  For me then i would consider myself on being rich when i do have 100 Bitcoins on which i could say that i can be able to make use of these funds to make up some offline business and making up some time deposits as well and having other option investment but if we do speak on just simply holding up your position then 100 pcs bitcoin on active spending or on a slow moderate kind of lifestyle on which if the price will really be that remaining or stay or wont go below 100k then this amount will really be making me live for next 40 years.

If you are living on a 3rd world country then you can be able to sustain up or you can be able to live with this amount if we do speak about fixed amount of Bitcoins with your hands but just like on what i have said that there's no such thing about fix amount because us human beings will really be wanting to have much as much as possible when it comes into your possession.People will always be that greedy and they are wanting as much as they can.

8 BTC is big one for many people and in many countries including first world nations. In countries like Nigeria, I really believe 8 bitcoins are too much for a retirement plan.

How many people on Earth have more than 1 bitcoin?

Not too many, and we can not identify this number but at least we know how many Bitcoin addresses that have 1+ bitcoin.
Bitcoin rich list https://bitinfocharts.com/top-100-richest-bitcoin-addresses.html

Check it with block explorer and its filter gives me 992,574 addresses.
https://blockchair.com/bitcoin/addresses?q=balance(100000000..)

The question is difficult to answer as one dose not have any idea on how the economy is going to turn out in the next few years, in some cases more btc might be required to sort out some circumstances, or less might be required, depends on the situation at hand.

And of course everyone would like to have as much btc as they can lay their hands on for retirement trust me, if i am asked how much btc I will be needing for retirement i might not be very sure with the answer to give, but i was thought to aim higher and think  big, so i will like to have as  mush btc as i can for retirement.

That's one thing, considering how things might change in the future, but there's also the obvious thing that people live all around the world, with very, very different costs of living, and also everyone has different lifestyles inside each different region...

So, it's really pretty much impossible to come up with a single number to answer this question.

It's almost irrelevant to say 1, 10, 100 BTC, etc, because in some cases it would be more than enough and in others not even close to match the lifestyle and cost of living.

600 dollars par mois pour une famille de 5 personnes ? Quel est le salaire moyen au Bengladesh par ailleurs ? C'est sûr que dans votre pays il faudra moins de bitcoins qu'aux USA ou en Europe ...

I found that : https://www.combien-coute.net/salaire-moyen/bangladesh/

Are you ok with those prices (in the link) ?

That's a tough question! It's impossible to know what Bitcoin will be worth in the future, and everyone's retirement needs are different.  I think it's smart to be realistic about what's achievable.

I agree that 10 Bitcoin is probably out of reach for most people, but even a smaller amount could make a significant difference in retirement.  Maybe we could try to figure out a more realistic target based on our individual circumstances.

Do you have any thoughts on what a reasonable amount of Bitcoin might be for retirement?  Maybe we can brainstorm some strategies for saving and investing in Bitcoin to reach that goal.

You cant say you dont know the amount of Bitcoin it would take for you to retire and live comfortably. There is no need for you to know what things will cost in the nearest future. The Bitcoin that will be giving to you now will be what will set you for retirement. You can use part to do business or you choose to hold some and diversify the rest into other assets. On a good day your Bitcoins should grow as time goes by unless you are one big spender.

I believe that when determining how much Bitcoin is enough for a secure old age, there is no point in looking decades ahead. It is enough to know how much money you need to spend per year of life at present. It is clear that someone can spend $1M per year, and someone will not spend $10k, because it all depends on the needs and standard of living.

Personally, I think that 10 BTC would be enough for me to live a good life.

If I have one BTC, I am very happy because I think one BTC is a lot. Now the price of Bitcoin has increased significantly compared to before, so now having one BTC means having a lot, although before the price of one Bitcoin was much lower, so at that time it was possible to own one Bitcoin with a little effort, but now it is not possible. Still, I am trying and trying to deposit at least one BTC in my wallet before retiring from Bitcoin investment. I know it is a big challenge for me, but still there is no problem in trying. I will keep trying, if I ever own one BTC, then I will definitely share that happy news on the forum.