FU status has traditionally been defined as saving 25x your annual expenses. If you have that much in bitcoin, you could probably pull the FU lever, but I think it's safer to go higher and do that at 30x your annual expenses. And for most people who can't do math, just use 30x your annual income.

If someone makes $25k a year, then the 25x and 30x level would be $625k and $750k respectively. If you actually have 15 BTC now and you only make $25k at your normie job, you might be able to pull it off before the end of this year, as you don't need to cash out all of it at once anyway. You can take out 1 BTC right now, still have 14, and survive for a couple of years regardless of where the markets go. But as Number Go Up ... ... you'll be in a much better position.