That's a bit tooo much lift for my taste, but NICE rig.
The auto's probably doing just fine, it doesn't see the daily grind of a normal every day vehicle. And sometimes I think, as long as normal service is followed and leaks do not go unattended to, too many people under-estimate these tranny's. I don't see any more failures in the 4L30-E then I see in the 4L60, or any other common tranny - as long as routine service is performed and the vehicle is not aggressively abused by constant quick WOT.
Towing, lifts, bigger tires, etc definitely don't help in the longetivity; but I haven't experienced any adverse effects - as of yet, with running bigger tires and towing for nearly 9yrs of it's life.
Most failures that I'm hearing/seeing of are coming from those that didn't perform service soon enough and/or had a leak that they chose to ignore.