It's hard to articulate. My family sometimes just calls it being a nudge or a repetitive pain the neck. The three-times-or-more thing seems to work very often because if it's something I want for my own benefit, people know i really care about it and if they're inclined to care that I care about it, they may take action. (Of course, if they don't give a damn about what I want anyway, it just annoys them but I'm rarely worse off than if I had never bought it up since I've only annoyed people who don't care what I want anyway.) If it's something I wish for and care deeply about for the other person's benefit, then they suspect that I'm going to hound them until they take steps to do something about it, and in many cases they'll do what they need to for themselves just a little more quickly just to avoid being nudged to the point of annoyance.