Let's face it, you're bleeders are trashed. It's not your fault, here's the problem; the 7x1 bleeders that come in your ATE caliper have a fairly long thread engagement and, they have a small 7mm hex head. After a while, these bleeders basically become "one" with the caliper as rust works it's magic and takes over. There is no way a 7mm wrench will ever be able to get that bleeder out. What happens? The small M7 hex gets rounded beyond recognition and you have a stuck or ruined bleeder.
Solution: New M7x1 bleeders with a slightly larger M8 head for better engagement upon removal. Well... that and the fact that you're going to promise yourself that you will change your brake fluid every year (at least). This way you can monitor the condition of your bleeder valves and, you can get new ones when needed (comeon... they're cheap insurance).