It works until it doesn't. And it can stop working very fast. Which is the scary part. But then it also depends on entry point. If you entered early even going down say 40% or 60% might not make you go red.
So if you want to invest in the top companies, you either need to think they won’t change anymore, or you need to find when to buy and sell.
Index funds solve this problem for you, albeit with slightly lower returns in the short term.
> So a viable strategy would be to only buy the best 7 stocks? Like the Dogs of the Dow, but reversed? (The Gods of the Dow?)
Or go with a NASDAQ 100 index: you'll generally get higher returns than the S&P 500 or Russell 3000, but you'll also get higher volatility. How well would you sleep at night with drops of -20% more often?
This is probably ok if you consistently sell stuff that exits the top7 and buy stuff that enters, but I kinda doubt it's all that much better. Same as the s&p500 and the Russell 5000 have really similar returns.
You'll be more exposed to screwing things up when companies enter/leave.