what happend re-define setInterval to variable in useEffect hook?

I want to know what happened if I define setInterval function repeatedly to same variable in react hook useEffect.

I checked variable have new setInterval id value every defining.
But I wonder is there instance remained in memory about previous setInterval timer, even if new setInterval defined at same variable??

 useEffect(() => {
    const timer = setInterval(
      () => {
        if (count < elementLength - 1) {
          boolean.current = false;
          setCount(prev => prev + 1);
        } else {
          boolean.current = true;
          setCount(0);
        }
      },
      boolean.current ? 50 : 2500
    );

    return () => {
      clearInterval(timer);
    };
  }, [count]);