Frequent back bearing replacement from long trips

I suspect you are using the wrong lubricant in the differential.  A Tahoe should be able to carry a considerable load without bearing problems.  Overloading will cause tire failure long before bearings are affected if the correct lubricant is used.  Locking and limited slip transmissions require a different lube.  If you have purchased new bearings from the same source each time I would consider a different source.  The failed bearings should be examined to try to determine the cause of failure.  I would check the lubricant level after driving a few hundred miles on the next trip. If the bearings are pressed on, I would also consider having them pressed on at a different shop.  They could be damaged during installation.

If your vehicle has a limited slip differential, it may require a different lubricant. Call the local Ford dealer parts or service department and ask.  to check the flluid level in the differential, you remove the plug on the differential case about 1/4 of the way down from the top.  put your little finger in the hole and bend it down. then remove and see if there is fluid near the top of the hole. (most service stations can do this for you).  If some lubricant runs out, it is full and no further checking is necessary. You don't need to take any with you.  your finger does not touch the fluid, don't drive far but, go to a dealer or large automotive service center and ask them to check and add some if necessary.  One 50 cent size drop is not a problem, but several may indicate a leak. Also, check on and under the back bumper after your trip and look for oil deposits (many wet spots) which can indicate a leak.