310 Bitcoin challenge has been solved

I also presume that you mean, the second time, that you sell 1/4 of the 3/4 you have left.

That strategy works for something like Bitcoin, if you got in near the beginning. It's a really nice strategy for that situation.

But let's say your employer gave you got stock options at $1/share which, at the time they were granted, was exactly the stock price. The stock slowly goes up to $2.50, then slowly falls to below $1.

There are two problems with your strategy in this scenario: First, when has it "doubled"? You were given these options for free, and (on the day they were granted), they are worth zero. As soon as the stock goes to $1.01, they've more than doubled... but you don't want to sell then. (This is also true of Bitcoins that you mined back when that was easy. They were essentially free, so when was the first doubling?)

But if you wait until the stock is worth $2 ("doubling" in another sense), then you only sell once, and only a quarter of your holdings. That's much less gain than you could have made.

Your strategy is a good one for a rocketship like Bitcoin. But you often don't know that you're on that kind of a rocketship until it's doubled several times. If you wait for confirmation that you're on a rocketship, you could miss some much smaller, but still really sweet gains.

What I did when I had the options scenario is essentially your strategy, but with much lower numbers. When the stock went up maybe 25% or 50%, I sold off some of the options. And some more when it went up another 25%. That worked very well for me. But if the stock had been a rocketship, I would have missed out on a lot.

That won't be true if the price goes high enough. By realistic counter example:

So you start when BTC is at about 10c. You mine around 2000 bitcoins (not bad, $200 for using your old 5870 that was collecting dust). Your card burns out so you quit mining, but implement the above strategy.

You sell 500 at 20c, 375 at 40c, 280 at 80c, etc.

Once bitcoin hits $13k, you have about 10btc left and have made $32k out of your possible gains of $20M.

I would say that less than 1 percent is not a sizeable fraction.

Of course, you would make a sizeable fraction if the price weren't able to double so many times, but the above example is actually quite realistic for some.

Then again, I've been beset with illness and medical bills, needing to pay for multiple surgeries, so I had little choice.

Not inherently. Only in the cases where it's a true choice between something revenue generating, and something people are doing for social good.

Your perception of social good (people dedicating their time to intellectual puzzles you deem worthy vs people wasting their time on these meaningless displays of skill), is different to someone else's.

My point was perhaps too broad - but deigning to tell someone their pursuit isn't as worthy as one you think they should be pursuing is, frankly, pointless.