I agree with taking backups. Since the only difference between full and free are the apps, you don't really need the full version.
Checking the changelog is the key to knowing whether you even need the full version if you're using one of the installed apps. If no changes are noted to the app portions, you don't necessarily need the full version at upgrade.
What you DO need the full versions subscription for is support and documentation access. As much as I've been using Zoo lately and feel at least at an "advanced" level, I find myself using the support forum and documentation regularly. So having a subscription is important from that standpoint.