Are you going to use a battery for power? How many volts and what size?
It must have enough capacity to provide the power to the piezo. Its capacity determines how long it lasts.
Then why use a lousy-sounding little piezo whistle instead of a real speaker driven from a powerful amplifier???
There are only a few 3V amplifiers available and their output power is very low. There are hundreds of more powerful amplifiers that operate from a 9V supply or are used in car radios at 14V.
I tied my circuit with an audio amplifier and a loadspeaker. But the reason that I'm more intrested in piezo is the cost. Actually the life is important too that I didn't consider. Which one has longer life, piezo or loudspeaker?
Speakers last a long time if they don't get wet, don't get poked or don't get burned.
Piezo transducers will be broken if they get poked or from too much power.
Speakers sound much better and cheap ones are available.