It's not that you need to keep upping the dose, it's that to combat the over training you have to keep upping the dose. And the over training gets worse the stronger you get. When your gains stall, decrease the volume, increase the intensity, and your gains will return, without upping the dose (to a point...).
It is true however, for very advanced people, there is a size you will seem to get to where nothing on earth will make you grow except upping the dose. But for the majority of people, they have not reached that point on their current dose.