Snapshots are a very handy tool for a System Administrator, but they can quickly turn into a nightmare if they are not managed properly. Snapshots take far more hard drive space than a virtual machine without, and if you don’t clean up your snapshots you may run out of drive space.
Figure: Snapshots are useful, but they can take up a lot of space
When you delete a snapshot you can no longer restore the virtual machine to the point in time the snapshot was taken. Deleting a snapshot does not affect any other snapshots, nor will it affect the current state of the virtual machine.
Set yourself a calendar reminder 3 weeks after you make a snapshot so you remember to apply the snapshot to the Virtual Machine (assuming you are happy with the virtual machine after the snapshot).