Which, according to the terms of Trek's limited lifetime warranty should not have been replaced.

Direct from the Trek website:
THIS WARRANTY DOES NOT COVER:
Normal wear and tear
Improper assembly
Improper follow-up maintenance
Installation of components, parts, or accessories not originally intended for or compatible with the bicycle as sold
Damage or failure due to accident, misuse, abuse, or neglect
Labor charges for part replacement or changeover
(emphasis mine)

So, your dealer basically did you a favour by getting it covered (twice, once at significant upgrade from the sound of it), or you weren't forthcoming with the deets of how the frame came to fall apart (which is a more likely situation.)

I work in Technical Support and deal with warranty situations for 40 hours a week. The game is the same whether it's someone's $50,000 portable ultrasound system that "just froze up for no reason and smoke came out the vents" or it's a $1000 bike that the frame "just snapped at the headtube/downtube weld for no reason".
When it arrives at the engineering bench for failure analysis, that's when we find the telltale signs of (in the case of the medical device) saline solution having been spilled on the system and huge scorch marks on the main board, or (in the case of the bike) metal stress indications of repeated abusive impacts.

Don't game the system, because what that does is help to hose the pricing for everyone by adding to the company's overhead with more warranty stock they have to carry, and/or makes companies develop more and more restrictive warranty policies like the one Surly has; which basically says, we'll determine whether or not what you say about our product failure is true or not... Before we decide to replace anything, because of exactly the situations I've outlined above.


Seriously, man. You broke an LHT. You pretty much have to hit one of the welds with a sledgehammer to break any of their bikes.