At the beginning of every new project, some bright spark will say 'this new website it should load quickly'. At this point, you should walk over to said person and slap them. Trust me on this, everyone will have a different definition of how 'quick' quick is.

Before you start looking at anything, I suggest you agree on an actual metric that's acceptable to everyone. If you’ve never heard of Jakob Neilsen, he’s the granddaddy UX guru.  In his research, he found that the bounce rate of people leaving your website dramatically increases over 3 seconds.  The longer people have to wait for a page to load the higher the change that they will give up on you. 

If people are leaving your website, you will lose out in sales, you can destroy the brand reputation and all that hard effort you put into your website is wasted. Speed matters.  Ideally, you want every page to your website to load in under one second.  Life will go on if your pages load in under 3. Anything longer and you need to make changes today.