Windows 7 - Firefox restore down button

Hello, I have Firefox 5.0 but this issue has happened with previous versions, anyway whenever I use the restore down button it never seems to remember how big I had the window before unless it's in a recent session but I if I had rebooted it goes back to default and pops out of maximize barely still displaying almost full screen. I sometimes want to access my desktop real quick as this is why I do this while maintaining a view of the window. Does it keeps this info cached somewhere?

It seems after a reboot it made a liar out of me. So now I'm not sure when it does it but I adjusted the window before and later on it does what I described above in the past. I'll have to pay attention the next time it happens.