Let me throw another small hand grenade into the discussion. Imagine that your company policy is not to land overweight unless it would be dangerous not to. Imagine also that when first aquired by your company the aircraft had a certificated weight of say 66 Tonnes.
Since they were not really using that landing weight the company then chose to re-certificate the aircraft to a lower max landing weight in order to save money. Guess what? The lower certificated landing weight now becomes the weight on which you are required to base your decisions.
So to summarise, last week you are not landing overweight, this week you are.