I'd agree with the above. I'd also note that the wear life of the brake pads is not brilliant in BB5 or BB7 calipers in that the brake pads are held off the disc by springs, and the springs sit within the thickness of the friction material. This means that Avid's recommendation is that the pads are replaced after only about one and bit mm is worn off them (from a friction material thickness of ~2.4mm) .
If BB5 (road) are set correctly with new pads, and the FPA/barrel adjuster are used as necessary there is enough arm movement such that the pads will
each wear about 2mm or so before you run out of arm travel. However if the brake is not set correctly to start with, or you somehow manage to wear the pads about twice as much as normal, the arm will run out of travel in a somewhat abrupt manner; the arm just hits an (invisible) end stop.
So with BB5 road, it is not at all a bad a idea to mark the caliper body with some blobs of paint so that you know if you are about to run out of arm travel or not. I think that BB7 do not have quite the same characteristic.
BTW it could be worse; Tektro managed to make thousands of calipers in which the end of the arm travel was signalled by a 'click' sound as the balls inside the calipers ran off the end of the ramps, leaving you with..... nothing....
cheers