I am currently evaluating adding CDN capability to our website. I know however I do not want to go through the effort, or pay the cost associated unless I can measure the improvements. So therefore, I need to make a measurement of the time to load the images on our site, before and after. Also some sort of indication of what to expect or a way to decide if I should even move forward and try integrating a CDN in the first place.
Right now I am taking all the different page types on our website, and taking note of the load time (cached, and non-cached) from the bottom right view on Firebug in the Net tab using the Images filter and recording it in notepad. After I get the CDN setup I will go back and review the results again. I also have a Google Analytics view grouped by the page type, and Avg page load time.
What I need to know if this method is consistent/robust/sound and/or prone to return inaccurate results.