According to CNBC, financial advisers are warning investors not to repeat dotcom-era mistakes as enthusiasm for the so-called Mag 7 and the tech-led U.S. stock market continues. JPMorgan CEO Jamie Dimon told CNBC Contributor Wilfred Frost on Monday that he would not buy stocks at current valuations, while Warren Buffett recently told CNBC's Becky Quick that it is tough to find value when everyone prefers gambling. Advisers said investors should start with a clear strategy, diversify across asset classes and sectors, and avoid putting too much of a portfolio into thematic or single-sector bets. Several said core holdings such as S&P 500 funds can provide meaningful technology exposure while still offering diversification, and that thematic positions should generally be limited to a smaller portion of equity exposure. They also cautioned that investors should consider tax consequences, including capital gains, before selling popular technology holdings.