Cached images

Hello,

I always surf using cached images only to make pages load faster and I  
manually load the images I want to see.
The questions is, why cached images are not preserved between sessions?
Here's an example.

1. Go to www.google.com.
2. Manually load the Google logo.
3. Close the page.
4. Empty page trash.
5. Go to www.google.com again.
6. Here, the Google logo is displayed since it was already cached. Which  
is OK.
7. Now, exit Opera.
8. Wait a moment. Make sure Opera is terminated (see Task Manager).
9. Relaunch Opera.
10. Go to www.google.com.
11. Now, the Google logo is not displayed. How come? Isn't it already  
cached?

BTW, these are my History settings:
- Memory cache = 2MB
- Disk cache = 20MB
- Empty on exit = Unchecked
- Check documents = Every hour
- Check images = Never

What I want is to make the cached images (and also documents) to be  
preserved between session.
Anyone have an idea where it may go wrong?
Thank you in advance.


Regards,