The isochron techniques are partly based on this principle.The use of different dating methods on the same rock is an excellent way to check the accuracy of age results.Radioactive decay rates have been measured for over sixty years now for many of the decay clocks without any observed changes.
Such failures may be due to laboratory errors (mistakes happen), unrecognized geologic factors (nature sometimes fools us), or misapplication of the techniques (no one is perfect).
We scientists who measure isotope ages do not rely entirely on the error estimates and the self-checking features of age diagnostic diagrams to evaluate the accuracy of radiometric ages.
A recent survey of the rubidium-strontium method found only about 30 cases, out of tens of thousands of published results, where a date determined using the proper procedures was subsequently found to be in error.
One question that sometimes arises here is how can scientists assume that rates of radioactivity have been constant over the great time spans involved.
Whenever possible we design an age study to take advantage of other ways of checking the reliability of the age measurements.