Attempt to more accurately measure Time On Site in Google Analytics by periodically phoning home to Google.

ga-time-on-site.js

;(function () {

var timer,
    interval =  20000, //      20s * 1000ms
    limit    = 300000, // 5m * 60s * 1000ms
    category = 'Time On Site',
    action   = 'Update';

timer = window.setInterval(function () {
    if ('ga' in window) {
        ga('send', 'event', category, action);
    } else if ('_gaq' in window) {
        _gaq.push(['_trackEvent', category, action]);
    }
}, interval);

window.setTimeout(function () {
    window.clearInterval(timer);
}, limit);


})();