The Alternate Backup type option alternates between backing up themes and extensions (add-ons), neither of which would let you restore your bookmark of course. As a full Firefox profile restores demands a second profile I recommend the less compact but much more flexible Selective backup including the additional items. FEBE performed excellent when testing.
In particular I like FEBE’s Backup reminder and its capability to schedule automatic backups, verify and save them in time-stamped folders. Last but not least does FEBE produce comprehensive result reports in HTML format, so if, for instance, something doesn’t right away you will easily spot it without digging through long inedible log files buried in a hard-to-find folder.
You may be surprised to hear that the FEBE Firefox Environment Backup Extension is capable to make a backup copy of common file and data used, but for the fact that the add-on isn’t cut out to handle system Windows files you may want to consider A more general backup software such as found in Bright Hub’s article Top Ten Free Backup Programs for Windows 7.
