Load balancing decision

It is an assumption based on a couple of decades of writing code.

Think about it, do you really care which one you get a response from, or do you just care that it has been more or less than 16 seconds since your last response? You only care if it has been more or less than 16 seconds. You don't care that 1, or 2, or all 3 have received a request. You just care that you have not received any response during the last 16 seconds.

If they are really keeping track of each outstanding check, then IMHO they are wasting resources.

Off hand, without giving it too much thought, what I would do is start a 16 second count timer, and reset it back to 16 every time I get a response. If the timer ever gets to zero, then change the status to down.