1)Sabayon is a rolling release. If installed once and updated regularly, you shouldn't need to reinstall new versions. Simply use the GUI package manager or command line if you choose, to keep up to date.
2)Sabayon is based on Gentoo's testing branch. Gentoo's testing branch is about on par with Debian's Sid (unstable branch) releases.
3)No big firm stands behind Sabayon.
You're not losing anything, please, be patient.