My original dream size was "bigger than my head", so I guess you could say I'm at my dream bust size already. That being said... my limit is based on being able to look after myself independently. Without a lifetime partner, I can't push myself beyond my own abilities or else I'll be in real trouble. I enjoy the struggles, but not being helpless (at least by myself ^^💦)
If limits were ignored, it'd be somewhere between the size I'm at now and the width of a double door. I don't think I'd want them extending down to my legs.