IIRC although the teeth get worn, this is the extreme condition and on the window regulators I've messed with, the center hole is elongated to the point where at the end of travel, it doesn't hold the gears together. Given access to a welder, this could be fixed by welding a heavy washer or two to carry the axle load, or putting some filler metal in the elongated hole and grinding it to the proper diameter. Not that I've ever done either of these, but suffered several wornout window regulators in my 2002 days.