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
Decreased performance if there are too many delta files in a chain (caused by having too many snapshots).
Decreased performance if delta files become too large.
Cannot increase Virtual Disk size while snapshots are active.
Delta files can grow to the same size as the original base disk file: a virtual machine's provisioned storage size can grow to ( its original size ) multiplied by ( the number of snapshots ).
Requesting a Snapshot
To request a snapshot for your VM, please use one of the following methods:
Use the VSS Portal - Request Virtual Machine Snapshot
Use the VSS Command Line Interface
Use the ITS Private Cloud RESTful API
Reverting to a Snapshot
To revert a VM to (or from) a specific snapshot, please use one of the following options:
Use the VSS Command Line Interface
Use the ITS Private Cloud RESTful API
Send an email to vss(at)eis.utoronto.ca
Deleting a Snapshot
To delete a snapshot for your VM, please use one of the following methods:
Use the VSS Command Line Interface
Use the ITS Private Cloud RESTful API
Send an email to vss(at)eis.utoronto.ca
Consolidate Disks
To consolidate VM disks, please use one of the following options:
Use the VSS Command Line Interface
Use the ITS Private Cloud RESTful API
Send an email to vss(at)eis.utoronto.ca
Recommended Reading
Understanding virtual machine snapshots in vSphere (VMware KB Article 1015180)
Best practices for virtual machine snapshots in the VMware environment (VMware KB Article 1025279)
How to consolidate disk snapshots (VMware KB article 2003638)
vSphere client: right click on the VM name, go to "Snapshots", choose "Consolidate".
vSphere Web client: click "Actions" tab, go to "All vCenter Actions", go to "Snapshots", choose "Consolidate".