What if I don't change my Master Cylinder on a disc conversion?

I swapped my front drums for disc and changed nothing else. Ran it that way for 8 years with zero safety issues. It wont empty the reservoir at all and the car will stop fine...just not as well as you would expect a disc brake car to stop. That being said, mc's are cheap and its a simple bolt on swap so buy the correct one, ditch the prop valve and it's good to go.