Testing, testing, 1, 2, 3...

It's a combination of AB testing and PRACTICE.

For a full routine, Rock tries hundreds (if not thousands) of preliminary ideas, out of which only a handful will make the final cut... By the time Rock reaches a big show— say an HBO special or an appearance on David Letterman— his jokes, opening, transitions, and closing have all been tested and retested rigorously. Developing an hour-long act takes even top comedians from six months to a year. If comedians are serious about success, they get on stage every night they can, especially when developing new material. They typically do so at least five nights per week, sometimes up to seven, and sweat over every element and word. And the cycle repeats, day in, day out.

It may not be 10,000 hours, but it is thousands of hours to get a single hour of material.

Wow.