Investing in bitcoin needs to be tailored to each person needs. While DCA strategy can work well for some. Each person has their own financial goals and comfort level with risk and investment timeline. It is also important to remember that people can change their investment approach as they learn and become more confident. Your example of someone starting with DCA and then switching to lump sum investment after learning more is great example of this. At the end most important thing is to find investment strategy that works for each person and allows them to buy bitcoin at their own pace without putting their finances in danger.
Because in Bitcoin investment, methods such as DCA or lump sump, it is just a person's approach to how to invest in Bitcoin and how they can adjust it according to their financial condition and their confidence. In the long run they can change their approach to investing in Bitcoin, they can choose DCA or lump sump, whichever is free, the most important thing is how they set their finances so that they can invest regularly and not sell just for short-term profit.
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A person who buys Bitcoin initially and holds for a long time, such type of investment is know as lump sum. And I see you might be misinterpreting it with DCA. I quite agree with you that they may benefits the most, but it depends on the amount invested at once and it's been held for a longer time. Let's say you bought 1 Bitcoin at initial stage maybe when it was $10 and you bought 2 for $20 and held till now you could most likely benefits alot from it as you said. But buying $50 Bitcoin now 1
BTC is equal to $104k at current rate will result to less or now sizable amount in the future.
The investor will be able to sustain his investment for a long time by diversifying little by little, which is why the DCA method is most important for both every holder and every investor.
I see you are misinterpreting diversification for DCA. We have 3 investment strategy, lump sum, buying dip and DCA. and DCA happens to to be 1 strategy for Bitcoin investment amonge the 3 type . While diversification means to diversify your investment in to different set or form of income generation. A person might decide to buy shears from bank , go into real estate and invest in Bitcoin or even decide to gamble %10 of his fund into altcoin, that is diversification. A way of investing in different form not putting all eggs in one basket.