One trick you can use, too, is to assign a different material to the current selection. Then, you can go into Surface mode later and right click the material and perform a "Select surfaces with this material".
You can do this for multiple materials at once with the "Select surfaces with material" plugin, if you're on Windows/Linux (
http://supercoldmilk.com/ac3dplug/selmat.html ).
Of course, if you've already assigned materials to your model, this may cause confusion.
I almost never assign materials to surfaces in AC3D, so I use this trick when I need to "save a selection". This also allows your "selection" to be saved with the model.