I have been taught that there should be an interval between making calls such as the fawn squeak. However, watching a rutting buck out in the field, I saw him respond when I was calling, but lose interest when I stopped. Would it be better to continue calling until an animal turns up?
The call-and-wait technique is widely accepted and generally has proved successful. The idea is to start quietly, in case a buck is lying close by, then by degrees call more loudly, varying the tone, but staying still between each session for several minutes. However, I can recall a number of occasions when a buck has lost interest, just as you describe.
A team of Swedish stalkers has recently been filming the roe rut in England, employing a new design of call. They were very successful using continuous, rather than spaced, calling. However, this was early in the rut and the bucks called were mostly young. A cautious buck might be alerted if, as he approached, repeated calling failed to be so convincing at shorter range, or was not accompanied by a waft of a does pheromones, for example. Bucks often circle to get the wind.
It is possible that old stagers might need a more refined technique before they are completely deceived, but there is a lot about calling which remains a mystery.