Brake Master Cylinder problems of the 2007 Cadillac Escalade

2007 Cadillac Escalade - required 2 brake jobs under 50k miles compared to 2004 Cadillac Escalade owned by same driver that didn't need brake work until approximately 90k miles. Driver is same for both vehicles, driving conditions for 2007 significantly improved, miles per calendar day, significantly less. Driver does not tailgate or, ride brakes. Dealer who's completed repairs has no explanation except possibly a hard brake situation(s) caused damage while brakes were heated up or, a hard brake situation(s) followed by the rotors getting wet, causing warp was issue. Dealer pushes concept that driver is issue (changed driving habits - more aggressive driving or, conditions) vs. Premature brake wear caused by quality of components. Dealer compares 2007 Escalade brake wear to that of a 2006 srx drove by same person which needed brake work at 39k miles. When asked if the master cylinder could be applying too much pressure to rotors, dealer said we could speculate all day but was confident the master cylinder pressure was not the problem and reverts discussion to driver. Seems odd since I drive fewer miles under less intense conditions. The 2004 Escalade - was a full time sales manager traveling on highly populated roadways - chicago, cincinnati, indianapolis, minneapolis, in 'rush hour' traffic. The 2007 Escalade - retired and drive minimally populated freeways and/or minor roadways in michigan. Have not contacted gm because previous discussions with gm on other matters were met by representatives who didn't view they had a role in correcting. An O2 sensor replaced when first purchased was told not warranty item as it was my responsibility to keep damage from occurring to it. Even though it's located outside/underneath vehicle and I have no knowledge of how to keep protected other than to ensure routine service. Heard it was no different than gm not being responsible for a rock hitting the window and cracking it. Appreciate your help!.