Welcome to the Sabayon Forums and to the Sabayon Community
Sabayon is a rolling distro, meaning that you will not need to reinstall your system, if you keep it updated, when a new version will come out, for example I have installed Sabayon 5.4 on this laptop and now, keeping it updated, I have Sabayon 6 on it.
Updated software will come naturally on Sabayon in the form of updates, that you can install, as any other software, with entropy. Sabayon has 2 package managers: portage and entropy. They are compatible, but it requires some experience to mix them correctly. For beginners it is better to stick with just one of them while, eventually, learning and getting to know the other one.
Portage, because of its source based nature, usually has the latest software available, entropy gets its binaries using precompiled portage packages, thus entropy gets its software after it is available on portage (and after some testing).
If there is a software that you want on entropy and it is not currently available, you can request for it to be added, following these guidelines: viewtopic.php?f=76&t=13891