Export Illustrator layers to separate Illustrator files?

Try this. Cut and paste into a text editor and save as a plain text file with a .jsx extension. You can either place it into your AICS4>Presets>Scripts folder and restart AI or just run it from File>Scripts>Other Scripts.

//////////////Start

var doc = app.activeDocument;
   
if (documents.length > 0){
       
    // Create the illusrtratorSaveOptions object to set the AI options
    var saveOpts = new IllustratorSaveOptions();
   
    // Setting IllustratorSaveOptions properties.
    saveOpts.embedLinkedFiles = true;
    saveOpts.fontSubsetThreshold = 0.0
    saveOpts.pdfCompatible = true

       
        if (doc.saved==false) doc.save();
       
        for (i=0; i<doc.layers.length; i++)
            if (doc.layers.locked == false) doc.layers.visible = false;
        fullDocName = doc.fullName;
        var param = doc.name.split('.');
        realDocName = param[0];
        for (i=0; i<doc.layers.length; i++){
            if (i-1<0) doc.layers.visible = true;
            else {
                doc.layers[i-1].visible = false;
                doc.layers.visible = true;
            }
            if (doc.layers.locked == false) {   
                docName = realDocName+doc.layers.name+".ai";   
                var saveName = new File ( doc.path + "/" + docName );
                doc.saveAs( saveName, saveOpts );
            }
        }
        doc.close(SaveOptions.DONOTSAVECHANGES);
        doc = null;
        app.open (fullDocName);
    }

/////////End