Url rules and performance

Hi all, I am currently setting up Url formatting for my website following the tutorial at: tutorial

I have a question regarding the following note:

"Note: Using URL rules will degrade application performance. This is because when parsing the request URL, CUrlManager will attempt to match it with each rule until one can be applied. The more the number of rules, the more the performance impact. Therefore, a high-traffic Web application should minimize its use of URL rules."

I was wondering how many rules a website with heavy traffic would need to have for this to start becoming an issue. I will most likely have around 15-20.

Any comments much appreciated!

In my web http://www.ho33.com, I use 17 rules, and it is extremely fast. Page size: 200KB, 27 http requests