Detailed yes long no, because they look at your medical information mostly. They want to see MRI's, scans, medications, doctors reports. They want proof. They briefly go over what you have to say. If they get twelve pages of whining with nothing to back it up you will most likely not succeed.

No one encouraged WHINING for 12 pages.

You specifically wrote "Try not to make it to long, because they are testing you the whole time. If you can sit and type out long letters than you can work." Some of us very strongly disagree with that advice. If detailed requires it being long, that is fine. Obviously, no one should whine for 12 pages......that is VERY different from cautioning people about "trying not to make it too long." It needs to be as long as it needs to be to give a clear picture to SSA of how the applicant's condition is disabling in their life.

SSA is capable of figuring out that an applicant may have typed or written all of that info over the course of weeks, so they would not reject a claim because the typed info proves they could do a job.