7 years is a tiny sample size if you are hoping to retire off it (unless of course you cash out your millions during that time). His advice makes sense if you are looking at a 30 year retirement horizon - it may not be there in 30 years.
Part of the beauty of index investing - names can rotate in and out of your benchmark based on whatever criteria the index uses (e.g. market value) but you're not bound to a company that drops from the index (you are, however, exposed between the time it becomes ineligible and the next rebalance).