I'm assuming you mean client side when you say "script side", in that case given you're running within a browser the browsers already have mechanism in place to reduce the latency as much as they can by caching static content or fetching content in parallel.

If you using Selenium to conduct testing you might want it to fail if the page doesn't load in X seconds. Keep in mind that nowdays "working" means not only that page loads but also that it does it in less than Y seconds. My recommendation is that you use timeouts to set bounds of the acceptable load times and whenever the test scripts fail is a sign that something is either broken or needs to be optimized in order to keep the user experience acceptable