It depends on the tire, but most are rated for 65 max. If the tires are rated higher and he doesn't mind the hit in gas mileage, ok. Having said that, most people I've talked to that run that fast totally ignore or are oblivious to either speed rating or tire pressure. These are the guys that blow tires regularly and blame it on "China bombs"..never mind that they were rolling 75 mph and 10 lbs under inflated.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition