If we look back at history, we can confirm that there have been 10 years of upward fluctuations in global stock prices.
1950s: German stock boom
1960s: US stock boom
1970s: Gold boom
1980s: Japanese stock boom
1990s: US dot com stock boom
2000s: BRICs boom
2010s: GAFAM boom
It has been repeated over and over again that a boom is born and then disappeared in a 10-year cycle in the global stock market. This may be because if one theme continues to be bought for 10 years, new buyers will not appear, and institutional investors will begin to relinquish their holdings thinking that no further returns can be expected.
There is also a possibility that people think of 10 years as a break in an era and unknowingly change their investment strategies.
In any case, if we look back on history, there is no such thing as a boom that lasts forever, so I don't think anyone will look at US high-tech stocks, starting with GAFAM, in the future.

Warren Buffett revealed that the holding ratio of shares of all five major trading companies, ITOCHU Corporation, Marubeni Corporation, Mitsui & Co., and Sumitomo Corporation, was raised to 7.4%.
＜Market capitalization＞ The amount in parentheses is 7.4%
ITOCHU Corporation: 6.73 trillion yen (498 billion yen)
Marubeni: 3.14 trillion yen (232.4 billion yen)
Mitsubishi Corporation: 7.08 trillion yen (523.9 billion yen)
Mitsui & Co.: 6.27 trillion yen (464 billion yen)
Sumitomo Corporation: 2.98 trillion yen (22.5 billion yen)
The total amount of shares of the five major trading companies held by Buffett is about 1.94 trillion yen (about 14.59 billion dollars), making it the sixth largest after about 2.98 trillion yen (about 22.4 billion dollars) of American Express (AXP).
With this, Japanese stocks have become the largest investment destination other than US stocks, but they are small when viewed from the Berkshire Hathaway portfolio as a whole (including listed stocks and unlisted stocks).