I agree and disagree with the previous poster. I am at a 00. My ears were pierced at 3 months old so they were LONG healed by the time i started gauging. My best friend wanted to gauge to a 00 as well, a tattoo shop in our city pierced him at a 12. It will hurt a shitload more than standard but it will also jump start you if you want to go big fast. As far as point of no return it all depends on your body, a good friend of mine could fit soda cans in his ears and he shrunk them down in about a year and a half to a size 10. he may need to get lobe surgery but that isnt too bad, i guess its an in office procedure where they freeze your "extra" lobe, cut it off, and sew the remaining two pieces together, doesnt hurt much more than the actual strecthing.
My personal advice would be when you strecth buy tapers, go slow, dont try to do big jumps, i usually went right in order. wait for all pain, soreness and redness to be gone before your next jump (i waited at least a week after all pain subsided.) play with them constantly teh day before a jump, lightly pull on your jewelry, try adding little things like sterilized safety pins (BUT DONT CUT YOURSELF!!!) then when you jump heat your ear with teh hottest water you can stand, a little vaseline on your lobe and they should slide right through. Dont force them because if they bleed it will make for a longer heal time, Also like the previous poster said you dont want to blow out because it hurts, looks shitty, and makes shrinking back down harder.