When you have your vacation set, your time will still run down as usual.
The only thing that the vacation status does for you is to prevent an opponent from claiming a time out victory against you when your time is totally depleted.
It DOES NOT stop the clock! So pay attention and make all your moves before your vacation period expires!
You can still make moves in your games while your vacation status is active, in case you were not aware of that.
This isn't explained very well in the FAQ
and is barely mentioned on the vacation settings page.
It probably should be stated more clearly or prominently in both places.