If you're cranking the torsion keys to raise the front end, you're raising the axle height relative to the position of the wheels, which increases the angle of the CV joints. Bigger angle means more flex with each rotation of the axle. More flex means more wear.
I'm not saying it will lead to immediate catastrophic failure of the CV joints, but it will contribute to an overall shorter life, to some extent.
So again, why do it? I guess I'm just a function over form guy. It's a tool. I don't spend my weekends making my hammers and screwdrivers look pretty, either.