Few observations from 2007 to till date
CO is conservative when there is a enough pipeline. He became aggressive when pipeline was drying in 2007 but that was once in a life time event and USCIS learned lesson.
Since then they do talk and now CO will be little aggressive when its running out of pre adjudicated cases, will do QSP as long as pipeline is not that big , if he build 2 years worth of pipeline then he may not do QSP for first year but will do for second.
QSP is not required as per INA so it up to CO.
If he builds buffer more than 8k then it will be tough for him to move in beginning of next year.