Most other prisoners of the early camps were soon set free again—not because of outside intervention, but because the authorities felt that a brief period of shock and awe was normally enough to force opponents into compliance. As a result, there was a rapid turnover in 1933, with the places of released prisoners quickly filled with new ones.

The duration of detention was unpredictable. Prisoners who expected to regain their freedom after a few days were mostly disappointed, but it was rare for them to remain inside for a year or more. Longer spells were served in the bigger, more permanent camps, but even in a large camp like Oranienburg, around two‐thirds of all prisoners stayed for less than three months.^244^

The result was a constant stream of former prisoners back into German society, and it was these men and women who would become the most important sources of private knowledge about the early camps.

(Emphasis added. Source.)