function aged(n, units, verbose)
n           - positive number
units       - time units: 'days', 'hours', 'minutes', etc
verbose     - print filename if file is too young

// Gruntfile.js

var aged = require('aged');
var files = ['Gruntfile.js', 'src/index.js'];

grunt.initConfig({
    complexity: {
        fresh: {
            src: files,
            options: {
                cyclomatic: 5,
                halstead: 10,
                maintainability: 100
            }
        },
        aged: {
            src: files,
            filter: aged(3, 'days', true),
            options: {
                errorsOnly: false,
                cyclomatic: 2,
                halstead: 10,
                maintainability: 100
            }
        }
    }
});

function fresher(n, units) {
    var isAged = aged(n, units);
    return function (filename) {
        return !isAged(filename);
    };
}