I have a Chicago Pneumatic 1/2" drive CP-744 I bought reconditioned from a Snap on tool guy who came to the garage back in the 70's that still works great. At the time I was told it was rated for 450-500 ft lb. and he gave me a one year guarantee. I've never had a problem with it. I also have a 3/8" drive Chicago Pneumatic as well.
Three years ago I was going to do a brake job on a friends car and he had just had new tires put on. The CP744 would not loosen about half of the lug nuts. I figured the 744 was getting tired after 30 plus years so 3 years ago I bought a Central Pneumatic Earthquake at HF for a little more torque (625 ft lb.). It had no problem loosening the remaining nuts. (They must have been put on with a similar gun) I bought it with the set of double sided impact sockets mainly used for lug nuts. I sent my CP744 to a local shop to have it checked and they said it tested at 425 ft lb. They were surprised it was over 30 years old and still had that power.
By the way, when I completed the brake job I manually torqued the lug nuts to proper specs and didn't use the gun like the tire stores do.