Promises in gulp.js for exiting after many async(?) tasks

gulpfile.js

//  gulpfile.js section
//
// ...
//
var gulp   = require('gulp'),
    Q      = require('q'),
    fs     = require('fs'),
    brands = ['gitHub', 'joyent', 'fractal'];

//	check the available brands folders
gulp.task('checkBrands', function(done, res){

	var deferred = Q.defer(),
	    brandsLeft = brands.length;
		
	brands.forEach(function(brand){
	
		var exists = fs.existsSync(brand);
		console.log(brand + ' ' + (exists ? 'found' : 'not found'));

		if(exists){
			existingBrands.push(brand);
		}

		brandsLeft -= 1;
		if(brandsLeft === 0){
			deferred.resolve();
		}
	});

	return deferred.promise;
});