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For example, let's say I start investing in Bitcoin in January 2025 and I plan to review the value of my accumulated Bitcoin in 2035. So what if I buy small amounts of Bitcoin regularly during this period? Then, even if the market price fluctuates at different times, it will achieve long-term growth for my investment, because Bitcoin has a long-term price growth trend.
Now suppose, I was trading during this period and sometimes bought Bitcoin and waited for the price to rise, and sometimes sold it immediately when the price fell, then my profit or loss would depend on the short-term market fluctuations. As a result, my risk exposure would be much higher. But, as a long-term investor, if I hold Bitcoin, even if the market drops a little, I will eventually achieve long-term growth.
I have no problem with your anticipation that the trader has a lot more uncertainties. It is possible that the trader could outperform the investor, yet it is way more likely that the trader will underperform the investor.
Regarding your specific example of 10 years investing, we might be able to control for how much a guy puts in and we might even anticipate raises every year, but let's say if the guy had invested $100 per week, then that would be $5,200 per year and $52k over 10 years, so then we would have a certain amount of certainty about the amount put in, we could likely have various scenarios on an Excel spreadsheet showing various possible BTC price trajectories, and we could get some ideas abut where the guy might be, even though surely we would not know the specifics until the time actually passed as compared with projecting in advance.
It seems much more feasible that any of us would be in a much more solid position to engage in persistent, consistent, ongoing and perhaps even aggressive buying of BTC (aka investing) rather than fucking around with trading that may or may not end up working out.