In most cases the defendant is in a panic mode after commiting a murder and has no real plan on the disposal of the body. In this case David E. and the girl just took off driving and probably considered a number of spots before settling for the spot just over the North Carolina line. Without the help of the girl it might have taken months to find the body.
Very often the perp is indeed in panic mode, which is why we often find sites at closer distances (one common number I've come across frequently is 20ish miles, I think they just want to get the body oUT of their car asap). However, depending on the experience, organization level of the killer, etc etc you will find a more thorough approach, say RAT who killed Alexis Murphy, (she has not been found). My guess with RAT is that he didn't just hurriedly dump her, but rather put more time and effort into her disposal, jmo. Also, premediation obviously can play a factor.
Awareness space can be a factor in the disposal though imo, whether instinctual, referring to non SK cases...
Link to article about awareness space, great article:
http://www.boulderweekly.com/news/j...-lsquoawareness-spacersquo-may-lead-to-clues/
*of course each case is different, but often a "familiar place" is gravitated towards imo. This also gives the perp a feeling of control, he can check upon it, etc.
It seems to me after reading AllisonM's first post linked above that Keepers might have gravitated towards her awareness space (even though, at this time, being a participant "after the fact").
Eta: ok, DE, not Keepers, sorry some confusion there, DE gravitated towards awareness space, AllisonM was referring to DE's relative, not Keepers. My bad, whatever the case...