In practice, the economic "long run" can happen exceedingly quickly. Keynes was probably closer to right with "Markets can remain irrational longer than you can remain solvent," but if you plan on the basis of "in the long run we are all dead," you might find out just how short that long run can be.
If we need to look to economics for rationality quotes, we are getting towards the bottom of the barrel, Robin Hanson notwithstanding.
Another month, another rationality quotes thread. The rules are: