"X" works as long as Firefox does a full shutdown when you close the last visible window. It's possible your Firefox has a hidden window or stubborn process that isn't actually closing until you shut down your system.

Could you investigate whether Firefox is still running after you close Firefox and allowing it 15 seconds to clean up? Here's how:

• Ctrl+Shift+Esc to launch the Task Manager
• Show More details if needed
• Click the "Details" icon in the left column
• Click the Name column heading to sort alphabetically

Do you see any firefox.exe process(es) still running? If so, I suggest adding the "Command Line" column (right-click any existing column heading, click Select Columns, then you can add a new column). The command line will show how that process was started.

You are correct. It begins debuffing memory, but does not complete shut down for some reason, even though I now have less tabs open than I used to. Not that ending the task does any good for it starting up properly next time.

Although I would be capable of carrying out some technical thing, I am afraid I don't know what you are asking about with command lines.

Okay, it's hard to explain how to investigate without knowing what is keeping it open. It would be safer to use Exit for the time being.