I think it depends of the period from the release of a new album.
Yesterday i watched an old show from 2003. And when i saw all the energy they did put in each of their words, i guessed it was from an early period of Meteora.
And yes, after looking the date, it was from the beginning of April (less than a month after the Meteora release).
Then you see that they put less energy with the time because it becames an automatism and they just do their job with less talking with the audience. Then they're ready to go to the next show...
It was the same thing when they were in Paris in May 2007 (a very few time after the MTM release), they're all have this fucking energy with the people and they were fucking happy to be there. And when i came back in Amneville in January 2008, there was 0 conversation and this show passed pretty quickly. It's the result of an automatism, that's too bad but that's life.
(sorry i came back with loads of words xD)
Oh and i voted the 2nd by the way.