In my case, our lawyer gave us instructions on what to write but wouldn't write it herself, since after all we know our case better than she does. She does go over the letter (s) and edit them. After that, which is where I am now with the waiver, she organizes all the evidence into exhibits and writes a brief using all the documents. According to the paralegal, the brief is gonna be around 20 pages long. The main hardship letter was three pages long though. It was heartfelt and to the point to not bore the immigration officer.

If someone is not using a lawyer I guess the hardship letter would be long as they would have to explain things in depth, but in my case, since the lawyer is writing a brief, it was not necessary to explain things twice.