I think it depends on your background but about 20 weeks into it I think you would be running very average times in races for your ability.
I think that how frequently you would be racing is an important additional factor here.
If you race every week or two and maintain that mental and physical edge, then you could do this for years and probably improve quite a bit and get to 80-85% of your potential, roughly (not even sure what that number means but its just my gut reaction). The tempo's and interval work and structure would get you to 100% in this example.
I think what happens, from experience, when you totally throw workouts and hard sustained running out the window on purpose and think " I am only running easy and strides " you can lose your "edge". When you get in a race it may be harder to push mentally, I think. An underrated benefit of periodic sustained hard running is the mental strengthening and additional comfort with running hard that you do not lose, say during a summer base building, but can be lost with 2-3 years without hard long running that really makes you go to that tough mental zone you need to access when racing. Sorry for the run on sentence.