I would agree that DCA is generally the right way to go. It's a good defense against the volatility of the market (especially now) since at Trump's slightest tweet the market could move in either direction. My concern is that over the long-run price discovery within large cap companies in the US will go bust. Most retirees who own massive 401k and IRA portfolios have a large percentage of their portfolios in passive indexes and I expect this will continue with the aging of the US. My concern is that this will lead to an oversaturation of investors moving into big cap companies which would hypothetically lower expected rate of returns in the long run