If you need a break from the interruptions, you can "Pause" StretchClock, and then you can un-pause it later:
Make sure you have the Firefox Add-on Bar enabled:
1) To show or hide the Add-on Bar, right-click on an empty section of the Tab Strip and check or uncheck it in the pop-up menu.
or you can use the keyboard shortcut Ctrl + /.
2) StretchClock should appear at the bottom of Firefox in your Tool Bar.
3) Press the "pause" button in your tool bar.
COMPLETELY REMOVING STRETCHCLOCK for Firefox
1) Open Firefox.
2) Click the Orange "Firefox" button (on Mac: Select "Tools" menu)
3) select "Add - ons"
4) From the add-ons window, click "Extensions"
5) Click "Remove" in the StretchClock section.