Powersurge,,,
I'm sure mike will pop in here, and I hope he does... I have talked to a Corvette Tranny shop before, and they told me this...
Always have YOUR tranny re-built, as transmissions wear to the harmonics, and vibrations of the vehicle it was mated to when it was a brand new unit...
I don't know if there is any truth to this, but I would rebuild yours... There are many hard parts that will get stressed that are not necessarily part of a rebuild... (Input Shaft Assy) ... For example, the input shaft (Steel) goes into an aluminum drum... After some miles, and hard driving, this area where the shaft and drum meet, can get really stressed, and eventually crack at the splined part...
Now, upon visual inspection of say a 4L60E with 50,000 miles, the technician may not see a problem with this part because it's intact, and not cracked or shows any signs of failre or fault... You just might get a rebuilt core with stressed parts ... Now you, POWERSURGE, trade in your practically new core for a used, re-built unit, and you don't know how THAT one was used... It may have hard use, and the part I mention for example might be stressed to 50,000 (more or less) miles already... I don't know if I'm entirely correct, but this is my vantage point...
11H