Retention, and why short retention fails.
THE PROBLEM WITH THREE DAYS
A site compromised with SEO spam may not be noticed for weeks. If you keep three days of backups, every copy you hold is already infected.
Short retention protects against yesterday's mistake and nothing else.
A SENSIBLE POLICY
Daily backups kept for a week or two Weekly backups kept for a month or two Monthly backups kept for a year
That covers recent mistakes, slow-burning problems, and the occasional need to retrieve something from months ago.
FOR SHOPS AND TRANSACTIONAL SITES
Keep more recent copies, since the cost of losing a day of orders is high.
FOR RECORDS OBLIGATIONS
If you have legal or tax obligations to retain records, those may require backups or exports kept considerably longer. Take advice on what applies.
MANAGING STORAGE
Automated retention that removes old copies is essential, or backups fill your storage and eventually fail silently.
THE MONTHLY COPY
The one people skip and most often need. Keep at least one.