I did some investigation as well and have found that although it is recommended that more is better, there is an optimum point where performance suffers as a result, now the only problem here is what is the optimim point ?, thats what I cant find
One thing to think about as well, is adjusting how often to update the page
Quote from Microsoft :-
While it's true that the more files you can load from your hard disk, the faster your browsing speed, it's also true that those pages on the Web might have changed since being stored on your computer. You might not want to miss fresh content just to save a little time. Fortunately, in addition to the size of the cache, you can also customize how often Internet Explorer checks the Web for updated content and downloads it to your computer.
The Settings dialog box offers three ways to check for newer versions of pages that are stored in the Temporary Internet Files folder:
Every visit to the page
You're assured of the most current content, but it's slower to browse previously viewed pages.
Every time you start Internet Explorer
Your first visit to a page will be checked, but subsequent visits in the same browsing session will not be checked.
Never
This option is fastest, but you could be viewing old content from the cache. To refresh the page, press F5 on your keyboard. You'll connect to the page on the Web. (This downloads the information to the Temporary Internet files folder.)
(Note: If a site has expiring content, such as news or sports, Internet Explorer checks for new content regardless of the setting.)
Try several combinations of these options and cache size to find the best fit for your needs. You may need to use the settings for a few days to fully gauge how they are working.