Serial Transmission Suddenly Gets Delay

Projects Programming
10 
[...]
String string = "";
int lastSample = 0;

[...]
void loop() 
{ 
  [...]
  if (millis() - lastSample >= 50) // We can't be overloading our computers serial buffer now can we?
  {
    Serial.println(string);
    lastSample = millis();
  }
[...]
}

I believe that lastSample should be unsigned long.

Regards,

Brad
KF7FER