userscript.user.js

// ==UserScript==
// @name        Paypal Sandbox autorefresh
// @description Automatically refresh paypal sandbox pages
// @include     https://paypalmanager.sandbox.paypal.com/*
// @include     https://developer.paypal.com/*
// @include     https://sandbox.paypal.com/*
// @include     https://www.sandbox.paypal.com/*
// @include     http://developer.paypal.com/*
// @author      Alex Le (http://marrily.com)
// ==/UserScript==

(function() {
  var refreshPeriod = 1000 * 60 * 5; // every 5 minutes
  var timer;
  window.onblur = function() { 
    timer = setTimeout( function() { 
      location.reload(true);
    }, refreshPeriod);
  }
  
  window.onfocus = function() { 
    clearTimerout(timer);
  }
})();