PrairieWind, imo, the desire will always be there. Once the threshold from fantasy to dark reality has been crossed, there is no turning back voluntarily, imo. It is synonymous to chasing the dragon in drug addiction scenarios, imo. There are many different scenarios and plausible explanations for a predator to temporarily quit killing, but the will to kill will always be there, imo...
Serial Killers - A Homicide Detective's Take
By Lieutenant Nelson Andreu (Retired)
Miami Police Department
http://www.expertlaw.com/library/investigators/serial_killers.html
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4. Victim Selection <Sniped & BBM -read more>
Unexpectedly, I have observed that most serial killers never actually find and kill their "dream victim."
Ignoring for a moment the disparity between deviant human and normal feline behavior, a serial killer can be compared to a hungry lion that lies in wait for his favorite meal. It may be the lion knows an impala has the most tender or tasty meat. He waits for an opportunity to kill and eat the impala and in doing so may allow easy but not-so-attractive prey to pass unmolested. In time, hunger pains growing and no impala in sight, the famished lion will settle for an unwary bird that happens by. After devouring the bird, which gives his hunger a brief respite, the lion again has time to savor the taste of an impala, and the cycle begins again.
Like the lion, a serial killer just will not defer acting out his urge to kill simply because his "ideal" victim refuses to materialize at his beck and call. But his reason for settling for something less divulges from that of the lion. There are two basic, interrelated reasons for this disparity. The first centers on the extra caution exercised by a serial killer in his search for a victim; the second, upon the nature of the compulsion that drives him to violence.