I would rather:
read a snappy rant about what's wrong with writers claiming that they can only "write long" when creating short fiction.
read an earnest attempt to help writers who believe that they can only "write long" when creating short fiction.
indulge in the self-flagellation method of my choice.
do something else that I will explain in thorough detail in the comments.
Note that you may not get your wish, but I look forward to reading your answer.