UPDATE:
1. I see that I can start the optimizer for a while, then click "STOP". This should be enough.
2. I am getting errors. I use the "WP Offload S3" plugin to store all my images on Amazon S3. Will this plugin handle that? The error log is showing messages like this...
I'd like to test this plugin on a small sample of my images rather than just let it loose on my entire blog.
Is there any way I can just limit the optimization to a small number of posts, rather than all of them?