(I speak about my company's SOPs for the 340 here - no idea about the other Busses, or other companies.)
If we have a dire emergency - an uncontrollable fire for instance - we will put the aeroplane on the ground ASAP, and to hell with the weight. (If there's an uncontrollable fire the aeroplane's probably going to be a write-off anyway.)
If it's not a dire emergency, all other things being equal,we will try and dump fuel down to max landing weight before landing.
However, if we do land overweight for whatever reason, then the engineers will do an overweight landing inspection. This is not necessarily a big deal, depending on the weight and rate of descent at touchdown it might only require a visual check.
One of the engineers told me the other day that 210 tons is the magic weight on the 340-300 - land below that weight and the inspection is no big deal, land above it and it becomes more complicated - but don't quote me on that, my memory might be wrong, or his gen. might have been duff.
Lastly, I did my initial 340 course at the factory in Toulouse and we were told there that the undercarriage had actually been designed with the -600 in mind and that even landing at MTOW would not do any major damage. (Always assuming that the rate of descend at touchdown is more or less normal, of course!!)
But to answer your question (now that I've actually read it properly
), the max landing weight is there for a purpose, we certainly don't ignore it just to save time and money. All else being equal, in a non-emrgency situation we will aim to land below max ldg weight.
Hope that helps. (And if anyone has got any other gen for the 340 -300, i'd like to hear it too.
)