Be careful with old versions!
These versions are displayed for reference and testing purposes. You should always use the latest version of an add-on.
The extension now works as I designed it from the start:
If you check the "autohide icon" option, the icon in the statusbar will appear only after defined times of firefox starts. In my opinion, the vacuum process must be done manually, but why should the icon be always visible? ;-)
This add-on is not compatible with your version of Firefox because of the following: