Don't wait for them to move away.

So let's say there's an uber hot guy that is exactly your type, but you shy away from flirting with him or giving your number because you have a boyfriend and are fully aware that's bad gf behavior. When you finally get out of your deadend relationship with your i-banker boyfriend you should pursue him. Otherwise you might discover one day that he's moving to (NYC/LA/SD) and the opportunity is lost. And every so often are reminded via social media that he's still hot, still completely your type, still a catch, but now across the country.