I would argue that EBS snapshots should not be used as a backup solution. EBS is reliable, but isn't engineered for the same durability as say, S3. These also become more unwieldy and less useful the older they get. Use EBS snapshots for rollback prior to making changes to your environment.

For durable backup I'd recommend storing objects in S3/Glacier. If you need to image an entire volume, make an AMI, which is stored in S3. Much more durable and targeted than a snapshot, and in the case of S3 objects, gives you benefits such as logging and version control.