How often to back up database

How often should I back up the MySQL database? Should it be everytime a new product is added, every time I backup my Zen Cart files or only when major changes are made. Does the database backup have to match the Zen Cart backup if I needed to do a full restore? IE do they have to be made at the same time. At present we are doing weekly backups of both. Thanks in advance.

I would backup the DB daily

It should be backed up daily by your host anyway but you should store your own backups and not rely on these should things go wrong.

as a host I back up daily, however I do n ot backup for YOUR convenience,
Customers are responsible for their own backups,
the backups we make are for server issues and as emergency backups,

it is a very good idea to back up your database daily and your files anytime you make a change

Yes Merlin, that is what I was trying to convey.
Theres no point crying to your host if the backup they have done for you is a bit old etc etc