A common belief is that 1) the biological and emotional aspects of sex are entirely independent, and 2) most sex is biologically complete and the same, and that it is the emotional or meaning aspect that fluctuates wildly.
This is because full discharge of sexual feeling is rare, and incomplete discharge of sexual feeling is not distinguished from complete discharge. This results in lack of satisfaction being denied or attributed to mysterious lacks in the relationship. Relationship and circumstances are critical of course: excitement and safety depend on them. However, factors internal to the person can often be the common aspect.
Promiscuity is usually attributed to strong 'sex drive' but is well expainable by the idea of partial discharge. A promiscuous person may well just be seeking full discharge but due to armor, he or she cannot achieve superimposition.