This isn't true actually. Of course there are exceptions, but from what I understand, typically a snake will shed, ~2 weeks later they'll ovulate, ~2 weeks after that they'll shed again, and then ~27-30 days after that they lay. That's why many people who aren't paying close attention to a snake will start to suspect they have a gravid snake on their hands when they shed twice in roughly a months time. Anywho, this is how my one snake did it, and from what I understand a pretty typical pattern.
Cheers,
-Matt