Hi
Basically, the photographs you view and edit in iPhoto are contained in a library. When the library becomes very large, with large images, iPhoto can become slower in operation. So the solution I described is to have more than one library - you can in fact have as many as you want. Your existing photographs, albums etc would stay just as they are, with the 8,000 photographs you mention.
The process I described would create a second library with zero photographs, which would then operate very quickly.
If you want to do anything with the original library, simply restart iPhoto while holding down the Option key and select the original library.
Having said all that, iPhoto should run well with 8,000 photographs. What version of iPhoto are you using? What Mac, and how much RAM?