Apollo 8 is not a very good example; it's not like the hardware pipeline wasn't well on its way to be ready to go by the time the decision was made.
Don't get me wrong, Apollo 8 was an extremely risky and critical part of the program, but it's not like somebody conjured everything up from thin air in 134 days.
Don't get me wrong, Apollo 8 was an extremely risky and critical part of the program, but it's not like somebody conjured everything up from thin air in 134 days.