Ok, I love big boobs as much as the next big boobs lover, but I think we crossed a line in how big boobs should get here.

My General Rule: If they don't sag to the ground then it's good to pound. Eh, just kidding. Really for me it's "as long as they are appealing". I think for most people there is a size limit. I have mine too. But over all it boils down to the fact that not all tiddes are drawn equally. There are some massive bust characters that work for me and others just don't. it's very case by case.
Now with all of that said I really wish people would stop underestimating how large breast can be made to be and large they can naturally get, especially on average sized women.