Without bushing the wheels to fit the hub snug you're asking the wheel studs to take the weight and not just clamp the wheels to the hub. This is not ideal partly because GM didn't want it done that way. Will it last? probably but I wouldn't advise running them like that.
Another concern is running true or not and being out of balance of not true. The fit on the studs is not as snug and precise as the intended fit on the hub, allowing for a little more runout.
Having driven a truck on the highway when all but one rear wheel stud broke off I can tell you it's no fun at all, and would be pretty terrible if they all break off.
