Not sure if this was mentioned yet, but if you're shopping for a used GX, grab the VIN and head to https://drivers.lexus.com/lexusdrivers/
There you can pull up the entire service history for any Lexus (if serviced at a dealer). I used this tool when buying my wife's 2014 LS460. Found one that had been to the dealer every 5k of it's 60k miles life. Every detailed service record was visible, and I knew we had a cream puff that was not neglected in any way.