If nox cat is re-coded replaced but sensor sends 200-400ppm, then yea relatively soon "Aging" code will be back. But if someone gets new OEM sensor AND does nox cat replace via ISTA, then I think it will be fine for another 100k.
The nox buildup in cat is tiny, its like microns thick layer. Definitely not "clogging" to cause back pressure, but enough so that cat does not work as expected anymore as the surface is "dirty".
There are other NOX emulators, after I bought NOXEM I noticed nox emulator on ebay I think it was 150 pounds or so, but I didn't look at it.
Also, what is this 138 pounds??
https://www.ebay.co.uk/itm/FOR-BMW-N...3/202798473696