Good point and one I hadn't considered.
Not an issue in my case because of the rather extreme nature of how I maintain my vehicles. Since I've got a lift, tire checking and rotation is a routine thing for every car and while the tires are off, I usually bleed the brakes and always check their condition. Usually taking off all the pads and giving them a quick cleanup on the wire wheel on the grinder since I use high-friction pads and I'm the only one in the family who doesn't mind their eventual noise.
Another caveat about topping off is that if your master cylinder reservoir is full when you replace your brake pads, and your brake pads were pretty thin, you're going to overflow the reservoir as you clamp the pistons down to make room for the new pads.
Ax me how I know. <g>
Speaking of damage to brakes, a track friend told us that he stopped to help a woman who was stranded at the side of the road with a locked up front wheel. The brake pedal was going down to the floor and a puddle was forming by one tire.
He pulled off that tire and couldn't figure out what he was looking at for a while. Said it was like looking into a cut-away of a turbo-charger.
Then he realized that what he was seeing was the inside vanes of the rotor. The woman had driven the car so long on no brake pads that it'd worn off the rotor surface (sounds unlikely, but perhaps they'd been turned pretty thin) and eventually the piston had come out of the caliper and gotten jammed in the vanes.
