Serial Port Communication

Can you see how you would ever leave this while() loop?

  while (Serial.available() >=0) {
    int inChar = Serial.read();
    if (isDigit(inChar)) {
      inString += (char)inChar; 
    }

    if (inChar == '\n') {          
      Serial.println(inString.toInt());
      inString = "";
      Serial.print("Please enter your age");
    }
  }