The widely repeated idea that Bitcoin will keep compounding 30–50% a year forever falls apart on the math, which is a reality check for anyone building a portfolio around it.

• The huge average return everyone quotes leans on Bitcoin's earliest days, when it traded at pennies and the whole market was tiny.
• Gains have shrunk every single cycle since, from tens of thousands of times your money down to under 8x in the cycle that ended last year.
• Running 30% a year for two decades would put Bitcoin's value at twice every public company on Earth combined; 50% a year gives a number bigger than all the money that exists.
• A more grounded 38% a year over the next decade would still be a big win, putting Bitcoin roughly where gold sits today.
• Shrinking percentage moves are normal for an asset getting bigger, not a sign Bitcoin is failing.

Outlook: Bitcoin can keep rising for years, but returns should keep cooling as it matures, so expectations built on the old compounding number are set too high.