You do not have to move your volumes: while the instance is in a "stopped" state...

saurik on July 31, 2011 | parent | context | favorite | on: 3rd largest Bitcoin exchange lost its wallet.dat

You do not have to move your volumes: while the instance is in a "stopped" state you can change it's instance type and then restart it. EBS-root let's you change hardware as fast as you can reboot with just three commands.