[CentOS] restart after yum update (6.6)?

Hi,

according to this :

http://unix.stackexchange.com/questions/28144/after-yum-update-is-it-a-good-idea-to-restart-the-server

i should reboot my server after updating packages i.e: kernel, glibc, libc.
Maybe it's a silly question, but Is it necessary if I don't use graphical environment ? (and don't want to use the latest kernel yet)