The strategy of making space between two girlfriends. By making time between the two, you let the heat die down from your ex, and hope that the girlfriend in the works will stick around. By waiting, you avoid a barrage of calls and facebook emails of the "OMFG WTF IS THAT SHIT" variety.
Dude 1: Hey, aren't you gonna go after that chick on 3rd floor now that you ditched whatsherface?
Dude 2: Yep, but the turnover rate is pushing one month.
Dude 1: I give it two weeks.