[Plugin: WP Super Cache] Every visitor generating a new cache file?

I seem to be having a strange issue. The installation went fine, no errors, .htaccess got updated etc. But when I view a page on my site, write down the timestamp and then check the same page on another computer a minute later, it doesn’t show the same timestamp.

Does that mean it’s not pulling the cached page but just generating a new one each time a given page is viewed?

Thanks a lot.