It is widely considered best practice to have your VMware Tools up to date and specially before upgrading the VMware hardware. As even the latest build versions within ESXi 5.5 have updates to VMware Tools this can often become tedious to manage. An easy way to automate this is to use the VMware Update manager.
If you have VMware Update manager already installed, Go to VMs and Templates view. From there you can select one of your customized folders or select the cluster. From there go to the Update manager tab, within that tab is the VMware Tools upgrade settings button. It will bring up window as bellow
Select all your VMs that you would like to have their VMware Tools upgraded at their next power cycle and vCenter will do it for you.
If you run mainly MS Windows, this comes very handy to plug in with your regular security patching restarts.