Yup, you appear to be one of the lucky ones, possibly on borrowed time. I had to rebuild my '96 trans twice before the 100,000 mi extended ran out, and long before I started modding and racing... just everyday squirreling around...
Now the '95 I've only had to rebuild once (so far) at about 25,000.. Up until about 2 years ago that was my mom's car and it had only 6,000 mi on it... It's never been raced or driven hard.. and I have a J-mod kit in the garage to put in her (the car not my mom)
From what I've read on this site the trans is the weakest link in terms of dependibilty and longevity (well, the original '96 intake ranks right up there) in our cars.
Sounds like you're anticipating that your's is gonna go and are all set to spend money on a new trans, and a J-mod... why not J-mod now and maybe your's won't crap out at all, and you can use the money you would have spent on a later model trans on something else... $200 of prevention is worth $1,000 of cure, no??? when you take it down to J-mod it, have someone that knows what he's looking at look it over and replace anything that needs it.
I actually don't really know what Max charges for a new late model trans (I guessed $1000 with labor, I know what a rebuild costs), but if you want to save you're money for the J-mod now, and wait for your trans to crap out, save up a bit more and you can get a Reinhart J-design Bullet Proof Trans for $1500.
Whichever way you go, consider adding an aftermarket trans cooler, if you don't already have one, and using Mecon V fluid in the new setup..
'96 T-Bird LX 4.6L Alive & well & living in S. Florida
N/A: Renegade NPI heads/Comp Cams; OEM intake manifold; Bolt-ons
245 rwhp; 13.713 @ 99.35 (Commerce, GA - November 2003)
BLOWN: Renegade NPI heads; Renegade shortblock; Intercooled T-Trim; some other stuff
Pump Gas Numbers - 547 rwhp / 525 ft.lbs; Best Time - 11.388 @ 118.68 (Commerce, GA - November 2007)