Im not expert, But why would your trans be going so quickly? I have a 93 Suburban. Its my daily driver. Bought it with 72K on the clock. Now have 231K. Never rebuilt the trans since I got it so my trans has at least 159K on it. I have towed a car on a dolly from NJ to Florida....and towed a boat from Nj to Florida. Truck tows my boat quite a few miles on the weekends in the summer. Truck goes into 4wd on the beach 20-30x a year. I chage fluid and filter 2x a year at beginning of my boating season and at the end. Never had a power flush. I dont hesitate to drive the truck at 80 mph on the highway, yet I dont accelerate real hard either... as a kid with my first TH700 equiped suburban I got sick of the cost to have trans rebuilt yearly, so I eased up on the peddle on acceleration. So I dont understand why your trans is blowing so quick. Is the truck equipped with a large cooler? If not it should.

I know it it was me I wouldnt bring your truck back to the shop who did it last rebuild, as they most likely did no uprgrades, and not quality work.