If you have instances in a VPC, they will keep their IP addresses until you destroy them. Turn them off for a week, then back on, and they bounce back with the same IP as before.<p>EC2 classic servers will also keep their IP addresses (and hence aws-assigned hostnames) through a <i>reboot</i> (in which the VM itself doesn&#x27;t actually get torn down), but not through a stop&#x2F;start cycle.<p>Edit: If your tool works for you, go for it. I don&#x27;t mean to sound discouraging.