To change the backup settings select Edit-->preferences from the main window. Then select the backup tab. This has a panel with a count specifying how frequently a playlist is backed up. The count is the number of edits before a backup occurs. If the value is 0 then no backups are made.
The browse button allows you to select a directory in which the backups are saved.
This is not a substitute for manually saving playlist to backup your work. Its main purpose is to provide a backup if the main data base becomes corrupted.