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

The best way and without any thinking is to just mine as many as you can you never know how many you'll be needing

You'd need a big ass pile of cash to start mining in a meaningful manner now. Those days are a pretty much gone for the little people.

The only realistic way to make Bitcoin that involves mining is mining the right altcoin and selling at the right time. Namely, mining altcoin number "8393589" while its cheap and easy. Wait for the pump. Sell right at the top. Profit.
If you did this with some coins such as Darkcoin, Nautiluscoin, Doge, Monero... and tons other, you could have made tons and tons of money.

So what you're saying is, if you guessed the lottery numbers correctly week after week, you could've made tons and tons of money.

I agree.

Of course is a lottery, but you have better odds than in regular lotery where it's raw luck. In the altcoin pump and dump business, you can take somewhat informed guesses on what is a good coin and what chances does it have to eventually get a decent pump. For example, right now Maidsafe is extremely undervalued. Buy tons over 10k and wait for a while until a big pump happens. Maidsafe is a legit and huge project that will go really far.