Just a very simple way to reset the 60-day eval licenses for a VMware home lab.
On the ESXi hosts
1) Open a shell to each host
2) Delete /etc/vmware/vmware.lic & license.cfg
3) restart services
1) Create a DSN to your local SQL Express instance that holds your vCenter DB.
2) Uninstall virtual center
3) Re-install virtual center and point to your DSN making sure not to overwrite.
With this method, I have been able to refresh my 4.1 and 5.0 hosts. Have not confirmed if this works for 5.1 first.