VM snapshots and concerns related to space usage are described in the Managing space used by snapshots recipe in Chapter 4, Improving Environment Efficiency. This recipe also has an example of configuring an alarm that can help to identify virtual machines that have a snapshot.
While such an approach is suitable for a cleaning task, it's also helpful to be notified about VMs with large snapshots before they take too much space and start causing performance issues. This can be achieved by creating an alarm with a higher threshold for snapshot size and attaching an email notification to it.
An alarm definition for snapshot size does not exist by default in vCenter and has to be added manually.