I actually really like your car, very nice!!
Now, I understand the total rock chip thing, I lived in Alberta for 8 years, so I understand the 'bra. That said, take it off whenever you are not going to be on the hiway or on (ahrggg) gravel roads. If you have the bra very clean and the car clean and waxed when you put it on and then take it off as soon as you can, the paint will last the longest.
If you leave it on, the slight movement of the top edge of the bra will combine with the dust in the air and wear the paint right down to the metal, and in some cases right into the metal over time.
Now, your choice on NFL teams, well....