I just had this happen recently and there was no warning. Perhaps it depends on the "level" of services you are using. My instance was just an "extra small" vm.
It's monthly, however even that isn't really acceptable. So far I've been too lazy to figure out if one can setup the live migration stuff to act as workaround for this...not sure. It's definitely something they should at least address / give an official workaround for, or preferably just transparently handle it.