Carbon 14 dating accurate?

basically as the q asks, is it accurate. Since we have only been able to study it for x amount of years, how can it be sure that there is no rapid point of decay and that it stays consistant. Like a car rolling down a slope, it starts slowly than speeds up, how to say it is consistant. I am bothered by the fact that it is used to dismount theories, when it is itself a theory without being proven. and if it has been proven, where are the 50,000 year old records marking the test that the rate of decay is constant for an eternity