I am using VMware ESXi. In our team we use to provide snapshots for long term backup.

Then we faced issues like memory spillover and the server got hang up.

I started reading in VMware knowledgebase articles and everywhere. Everywhere it was recommended not to have snapshots for a long time.

Even VMware advised to keep snapshots for maximum of three days.

But our team kept asking us to have at least two permanent snapshots (till deleting the VM). Sometimes we may use the VM for a year).

1. one snapshot is for fresh machine state. (So when we complete testing an application, we will revert back to fresh state and install another application) (If I did not allow that, I may often need to host the VM.)

2. Next snapshot for keeping the VM in some state (maybe they would have found an issue and keep that state for some time. Or they may install prerequisites for the application and keep the machine ready for testing.)

Logically, their needs seems to be fair. But if I allow that, I am to permit them to hold the snapshots for long time. We are not using our VM as a mail server or database server.

Why is keeping snapshots for long time having an adverse effect?

Why are snapshots considered as temporary backups, not real backups?