It sounds like a person as SMART as you would realize nothing last forever even with proper service...
But it sure can extend the life of alot of things.....
Okay smart-a$$... as if I meant "forever" literally.
It's a figure of speech for a very long time.
I'm by no means a know-it-all. Never said I was.
If Howard Clayton managed to get 1.4 million miles out of one NV5600, and it still works perfect... then I would consider that "forever" enough to call it forever.
Once you fix the 5th gear nut on a NV4500, it shouldn't live any shorter a life than an NV5600.
Even with proper service, there are things you shouldn't do while driving... things that will damage an NV4500... like repeatedly using your clutch to slow you down. Or pulling a 20,000Lb trailer up a hill in 5th gear at WOT.
And just because your O/D bearing went out doesn't mean you need a new NV4500. So you R&R it and your tranny is back in business. It's not like you need a replacement!
In Phantom's original post, he said his tranny was "trashed" after 325K miles. That would lead one to believe he needs a replacement, not a rebuild.
325K would be a lot of miles on a stock 47re/rh automatic, but that's quite a short life for a NV4500.