When you shift from customer development to company-building. In other words, when you stop searching for, and instead start scaling, a business model. See also: http://steveblank.com/2012/03/05/search-versus-execute/

When 0.1%-10% of equity is no longer in the cards for high value front-line (not VP) employees.

After about 1-2 years.

It is like saying that your car or house is new after 10 years. Or saying your shoes are new when they are 6 months old.

The word is pretty self-explanatory, it is not that hard people.

When you are too big to pivot.