What if you are the unluckiest person in the world with $1M and decided to invest in QQQ in March 2000? The 30y treasure at that time was 6.5%, so you put 70% in QQQ, and 30% in treauure. After that, you were scared to death and never invested another penny.
This is what your portolio would look like over the years
1: By 2002 (worst time), gain 13% in treasure and lose 80% in QQQ = $480k
2: By 2007, gain 45% in treausre and lose 50% in QQQ = 780K
3: By 2015, gain 100% in treasure and make even in QQQ = $1.3M
4: Today, gain 156% in treasure and 4x QQQ = $3.5M