You guys with K2s and transmissions going out, did you know that the transmission has a thermostat? This thermostat keeps the temperature as high as the engine which kills them. Either "Flip the Pill" or put in the new, lower temperature thermostat that GM recently released. Also, don't let your fluid run past 50K miles. Follow the severe service schedule regardless.
The previous generation trucks usually start to fail at 166K after no service and will easily run into the 200s with regular maintenance. We've seen more than a few 6-speeds hit 300K and one just over 400K miles. This tip applies to all of the transmissions used, 6-speeds, 8-speeds and 10-speeds.
Gary, sorry to hear about yours, we know you take meticulous care of it.