Question about Ultrasonic Sensor Delays and Millis

In many datasheets for Ultrasonic sensors, I see a 40ms to 60 ms delay for pinging should be implemented but nearly ALL examples I have seen do not use this delay. Are there any issues that occur if you do not implement this delay ?

(deleted)

Thanks. I wrote this code to add in the delay.

double distance(bool Ping = false) {
  double distancecm = 0;
  unsigned long Ping;
  

  if (Ping || (millis() - savedDist >= 50)) { 
    digitalWrite(trig, LOW);
    delayMicroseconds(2);
    digitalWrite(trig, HIGH);
    delayMicroseconds(10);
    digitalWrite(trig, LOW);
    distancecm = pulseIn(echo, HIGH) * 0.034 / 2;
    savedDist = millis();
  }
  return distancecm;
}

I don’t have any hardware to test right now, but is this correct ? Is there any demo code with the 40ms delay for an ultrasonic sensor ??

Or should I just add a millisecond delay which will run every single time it is called. Is the ms delay a better solution or the code on the top ?