I ponder that sometimes too. Then I try to think back on when I was in high school. Wasn't there like a three day rule or something? Then I realize that I'm not in high school and I don't need to play games or make rules anymore. I say, call when you want. That night, the next day, in a week. I don't think you should worry about if you are going to be too agressive or pushing them away. That's just me.