I do not agree
My personal opinion is linking to that many JavaScript and CSS resources is a very bad idea and waiting for a problem is also another bad idea. One of my jobs was to decrease the load time of a website. The first time the page loaded, it took the site about 45 seconds to fully load. Who in their right mind would wait that long for a website? lol. I got the website to load under 10 seconds, I could have gone further, but the head guys refused to lazy load content.
Why I do not agree
You may never see the problem on your network. You are sitting close to the servers that host your site and you are probably also on a fast connection. Your users might be sitting on the other side of the world on a slow connection. That is a double whammy. This means the users on the ther site of the globe will see bad performance and you will never know unless you do some fancy clientside logging [like I tend to do] or you have a helpdesk that hears complaints all the time.
Why there is a problem
The reason why we want to limit http connections is that older browsers allow only 2 concurrent connections at the same time. That means you have scripts, images, css, etc all fighting for those two open connections. BUT it is a double edge sword when you reduce the number of files by concatenating them. the reason is the file sizes increase.
The improvements
The first thing I would do is to make sure that you are using compressed files. This will reduce the amount of data that will be transferred. Whitespace and Comments mean nothing to the users. Also make sure you are gzipping the files.
The second thing is to make sure that your files are being properly cached. You do not want your users to be forced to download the files [ or check to see if they have been updated] every time the page is loaded in the browser. This way the users only have a penalty the first time they use the site.
The third thing I would do is create cnames. The 2 connection limit I talked about above is per domain. If you create subdomains such as static1.example.com, static2.example.com, and so on. You are getting 2 more connections per cname. Do not go all crazy an make 100's of sub domains because there is a limit to performance. Most studies said 4 is normally the sweet number. This is a big boost for most sites
The fourth thing is to lazy load anything that you do not need right away. If the user is not going to use script XXX as soon as the page is loaded, than why load it on the initial load. After the page is ready, add it dynamically.
The fifth thing is to dump window.onload and move to document.ready or loading scripts after the body content. The reason why window.onload is bad is it has to wait for EVERYTHING to load fully. That means if an image hangs for some reason, your JavaScript will sit there and wait until it times out/errors or loads. One hicccup on the server and your site can become a snail.
The sixth thing, load your JavaScript resources at the bottom of the body. Sounds weird, but with the way the browser renders content, it boosts performance.
Wrapping up
I know I went a little overboard on this and probably answered something totally different than what was asked. Load time is very important. Why is it? First your users do not want to sit around and wait. I personally will leave a site if it takes forever to load. The second reason why website load time became even a bigger factor was when Google started to use load times as part of their ranking score. Slower sites means poorer ranking.
Tools such as
YSLow will give you guidelines to follow to speed up your site and give you a score.
Time for me to crawl back into my hole.
Eric