You can think of a snapshot as a bit-by-bit copy of a disk device: like if you issue the
dd command to clone a partition, the output file will be the size of the whole partition. Because of the technology used under the hood, creating a snapshot is quite fast, and boot process is not different than booting from another image.
You should be able to take a snapshot, delete the instance and boot it up again later but the reliability of this process depends on how the image is built, customized. You may want to run some tests first to make sure, like take a snapshot and boot it (before you destroy the running VM).