I run nightly, weekly and monthly backups for the filesystem, and for databases. These should happen on the same schedule so that when you need to restore a site from backups, the database and the files are in sync with each other.

For example, Craft CMS stores a record in the database of which Assets (files) exist. If the database backup and the file backup are taken 5 days apart, those will not match, and some images may not exist that Craft is expecting to be there.

Currently:

• Monthly File backups happen on the 1st of each month
• Monthly Database backups happen monthly on whatever day you set them up (so if that was the 15th, it'll be 15 days out of sync the last file backup)

There's been a couple of times recently where I've needed to restore a site from a monthly backup - and the files / database are out of sync because I set them both up on the 5th of the month.

Files:

Databases:

These should ideally be completely identical. But if the file backups don't need to happen as granuarlly as the database backups, at least the nightly, weekly and monthly backup schedules should happen on the same schedule.