23 February 1995: The Dow closes above 4,000

The Dow Jones Industrial Average closed above 4,000 for the first time, at 4,003.33. It had taken decades to get from 1,000 to 4,000, yet the next milestones came at dizzying speed: 5,000 that November, and 10,000 just four years later. Investors who bailed out in 1995 because stocks looked expensive missed one of the greatest bull markets in history. Expensive can always get more expensive.

The lesson: Valuation alone is a poor timing tool; markets can stay pricey for far longer than you expect.