I've got a buddy with a 4L60E in a 1500 Suburban that is near 300k with no issues. I had a 99 Silverado with a 4L60E that very early in life had an issue with the sun shell that was considered a defect and was fixed under warranty. After that, I drove it to about 120k before selling it to my secretary. Her husband still has it and it is approaching 300k with no major repairs on anything, including no issues with the engine or transmission. Man, I miss that truck. It had the original 270hp version of the 5.3, but for some reason, felt stronger than the most recent 1500 Silverados I've driven with the 5.3. Maybe the truck was much lighter. I don't know, but that 99 hauled the bacon. Great truck.
I had a 2008 15 passenger Chevy van with the 4L80E. It had some kind of problem and my wife ignored the warning light, finally pulling over when it was bucking and lurching. I don't remember what the problem was, but the tech told me that if she'd heeded the light, it would have been a simple repair. Because she didn't, it dumped the fluid and ate itself. Remarkably, with 115k on it, which was well past the warranty, GM agreed to cover the transmission if I paid the labor. Done. (I never asked them to warrant it, knowing my wife contributed to its untimely demise.) We traded that van about a year later on our Transit 350. Btw, I towed a 26' deck boat with that Chevy. It was a brute and was long as a semi with that boat on the back, but it towed that big boat very well.