The stresses of driving (accelerating, braking, turning, hitting bumps in the pavement), etc are what's going to do damage to your alignment. The fact that the front sits lower than the rear isn't something that will change over time; it's not as if the rear will start sagging. That's a product of how the suspension is set up and the physical geometry of the parts, not an alignment -- in fact what you're asking about isn't even something that's addressed in an alignment, which focuses solely on the absolute and relative orientations of the wheels.
