What is the impact of adding a floating IP to an active HA LTM pair?

I am assuming if you don't define the floating address for the network when it fails over that particular subnet vips will not be reachable because there is no one to handover or repoint to the stby ltm...where as the vips on the subnet where floating is enabled will not have any issues. In my environment we make sure that floating is defined on all the subnets we are using.