Seeing What Updates were Applied

When I log into my clients WHM I see the yellow bar across the top, 'You must reboot the server to apply software updates'. How do I see what updates were applied, so I can decide whether to reboot the server? Does grep -i 'updated' /var/cpanel/updatelogs/ give the full story, or only any updates applied on the date of that log? I have read from other forum postings that a server should only be rebooted following kernel updates (if thats your preference of course). How do other people approach reboots?