Aperture has a nice feature; it allows you to duplicate a project structure. Let's say you have a project with a few folders and smart albums inside. Now you have a similar project and want to recreate that structure: just right-click on that project and select: Duplicate Project Structure. Unfortunately if your starting point is a folder, there is no “duplicate folder structure”.

Here is a workaround:

1. Create an empty “dummy” project.
2. Inside that project, create the folder structure you want to duplicate. You may add folders, projects, and Smart Albums.
3. Now right-click on your project and choose Duplicate Project Structure
4. Rename the folder to whatever you want, move it from the duplicated dummy project, and delete the duplicated project.
5. Keep the original “dummy” project so you can create multiple similar folder structures.

The “Duplicate Project Structure” feature is very handy, but unfortunately can only be used on Projects, and not Folders

This is how I use this on my workflow: I have a folder for each year with a subfolder for each month, and inside of that, projects for each photo shoot / event / trip. Every year I duplicate that so I don't have to create folders again for each month. 

I hope you find this tip useful!