He's managed to do very well with little diversification by industry. In fact, I believe in buy and hold even more now than I did a year ago. However, I've seen buy and hold misconstrued more and more in the past year, sometimes grossly so. If you buy a poor quality company or pay too much, holding on to your position for years and years won't necessarily bail you out. But finding great businesses run by smart people, buying them at a discount to their intrinsic values, and holding onto them is still one of the best strategies out there.
Price fluctuations steal the headlines in the short-term.
But over long stretches of time, fundamental value still carries the day. I don't see how last year's events do anything but reinforce that thinking. The answer is nine years, and we're already a year away from when the Nasdaq first hit 5000. So, I think that's one way of framing some of your views on expectations, and buy and hold approaches generally. We'll just have to come back in nine years and see.