Good purchase! Mine have the 620 treadwear rating too and they are pretty worn out at 30k miles, probably have another 10k in them, 5 at the worst. Same as the 440 rated MXV4+. I'm happy with that life too...
Sorry to be blunt but the Goodyear Integrity tires suck. We had them on the Prius and they are awful, terrible ride and noise, zero wet weather traction, really soft sidewalls affording sloppy turn in etc. It would be a crime to put those tires on an LS IMHO. I would never even buy another set for the Prius.
That would be inadvisable since the OEM tire size for his 2000 LS400 is 225 60R16.