What is End of Life for CentOS 4?

End of Maintenance Phase for CentOS 4 is Feb 29, 2012. You should plan to upgrade your vps/servers to new OS in 2011.

Note: CentOS 5 brings nothing new for a VPS. Most of the features introduced in CentOS 5 are for full-fledged dedicated servers e.g. clusters, virtualization.