According VSS best practices (based on VMware best practices), the maximum lifetime for a VM snapshot should be 72 hours.

Snapshots are NOT backups

A virtual machine snapshot is not a copy so it cannot be treated as a direct backup. A snapshot file is simply a log of changes to the original virtual disk. The virtual machine is running on the most current snapshot, not the original vmdk disk files. To reiterate: snapshots are not copies of the VM's original vmdk disk files. Taking a snapshot does not create a complete copy of the original vmdk disk file, rather it only copies the delta disks.

Side effects of running with snapshots

Requesting a Snapshot

To request a snapshot for your VM, please use one of the following methods:

Reverting to a Snapshot

To revert a VM to (or from) a specific snapshot, please use one of the following options:

Deleting a Snapshot

To delete a snapshot for your VM, please use one of the following methods:

Consolidate Disks 

To consolidate VM disks, please use one of the following options:

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