I have an 06, in sig. Mine is all stock. Trans makes some noise but functions perfectly. I will drive it till it dies then rebuild it with a few upgraded components for the sake of longevity only. I will not be increasing the power of the engine.
The 48RE was designed as a match for the stock 5.9CTD engine. It cannot handle increased power if you have any add ons for your engine.
Basically for the 48RE you drive it till it wears out. Then rebuild it and when you rebuild there are certain components that should be replaced with mildly upgraded parts then the trans will be near bullet proof. I know many who recommend a minimum of upgraded converter, valve bodies and upgraded bands/drums. Other parts get replaced as needed.