To point number 1: Depending on what sort of work the subject is doing with the clearance, he/she may never get a poly, or he/she may get one every time the cl

To point number 1: Depending on what sort of work the subject is doing with the clearance, he/she may never get a poly, or he/she may get one every time the clearance is updated (usually 5 years). If the subject happens to be living with a foreign national, and somebody writes a "letter of compelling need" for the subject (meaning the subject will retain the clearance in spite of the risk), then the subject will get a poly every year. The poly is not limited to one session. The examiner will keep asking the subject to come back until they are satisfied with the results, or until the subject quits their job. Depending on the personality type of the subject, it can be extremely stressful, or just routine. Many engineers are "Type A" and that is the type most susceptible to stress.