IMO, based only my observations of Jake in court yesterday and also by having read the transcript of the Criminal Complaint, I believe Jake is arrogant and self-confident, violent and cold blooded and very, very, very calculating.
I am of the opinion Jake had been planning or fantasizing about abducting for quite some time, perhaps months or years, before picking Jayme as the one. I believe his plan did include what his exact intentions were for her and what his exit strategy was going to be once he decided the time to exit was right. I do not believe Jake returned to his home and removed Jayme from the trunk and then said to himself "now what?" Nor do I believe he had any intention of wanting someone to play house with.
Given Jake maintains a relationship with his parents and Grandmother and possibly others, regardless of the nature of their relationships, I believe from the get go that Jake calculated out and knew all along that he would only be able to keep Jayme for "awhile", as with time he knew he stood more of a chance of being found out.
I believe Jake had the intention from the get go to eventually kill Jayme and dispose of her remains. Jake has no compassion whatsoever, as one can easily determine by reading the criminal complaint. IMO, Jayme's days were numbered from day one. I also believe Jake loved following the case through the media and took great pride in what he believed "he got away with". I believe he would have disposed of Jayme in a manner that would make it difficult to locate her remains for a long time, if not forever. Or, alternately, he would have disposed of her in away that would allow her remains to be stumbled upon which would allow him several more months of the media discussing Jayme Closs whilst he patted himself on the back gloating about what a mastermind he was and how stupid everyone else was.
And with time I have no doubt he would have been out hunting for his next victim. I believe he would have continued on to be a serial killer/ abductor.
But who knows..............and I am of course only speculating and am expressing my opinion only. Thankfully Jayme escaped, I do believe her days were numbered.