How to export a sequence of layers in illustrator?

I often have to modify pdf files and show them in stages. Like this:

First:

Second:

Third:

I'm currently doing it by separating each part of the plot into layers and then hiding some of them, and exporting them to as image files. Is there a more convenient way to do this? I don't want to duplicate objects into different layers because if further along I want to make changes, I'd have to them on every layer.