I've also wondered how much TTU takes into account past history... for instance, there are people that b*tch, whine, and moan about everything (the squeaky wheels, so to speak) and others who barely speak up. I've had two occasions in the past year where I've been p*ssed off enough to write, and they did OK in my book for me (5k miles for a lost baggage incident, 25k miles for non-functioning AVOD and electric in Y traveling AMS-MSP).
If they see a pattern of constantly griping, I would imagine they would stop being so generous... correct?
I've wondered this myself. I am curious if they see a record of a customer's past complaints when they consider what to offer.
In my case I've only sent one TTU in the past several years, so that shouldn't have made much of a difference here.
UA on the other hand hears from me a lot more often, their planes are in terrible shape. They usually hand out anywhere from $100-200 in vouchers pretty easily, and that's in coach.