Radiometric dating methods reliability
It is more accurate for shorter time periods (e.g., hundreds of years) during which control variables are less likely to change.
There are a number of implausible assumptions involved in radiometric dating with respect to long time periods.
Another assumption is that the rate of decay is constant over long periods of time.
Radiometric dating requires that the decay rates of the isotopes involved be accurately known, and that there is confidence that these decay rates are constant. The physical constants (nucleon masses, fine structure constant) involved in radioactive decay are well characterized, and the processes are well understood.
Electron capture requires that there be an electron in the vicinity of the nucleus, so its activity depends strongly on the configuration of the electron cloud, which depends on the chemical state.
In fact, it is possible to shut down electron capture completely—simply ionize the substance so that there are no electrons nearby.
There are a few effects that can alter radioactive half-lives, but they are mostly well understood, and in any case would not materially affect the radiometric dating results.
That is, the analysis of the isotopic and chemical composition of the sample has far greater uncertainty than any uncertainty in the decay rate itself.
We can now calibrate this out by looking at C14 in tree rings of a known age - but the charge of "C14 dates are wrong" is used by nutters (sorry creationists) either deliberately or in ignorance.
Recognizing this problem, scientists try to focus on rocks that do not contain the decay product originally.
For example, in uranium-lead dating, they use rocks containing zircon (Zr Si O Zircon and baddeleyite incorporate uranium atoms into their crystalline structure as substitutes for zirconium, but strongly reject lead.
And one thing that the young Earth creationists need to explain if they're going to be down on radiometric dating--why do all subterranean pieces of dead organic matter have lower relative abundances of Carbon-14 than ones exposed to the atmosphere?
What is their proposed mechanism for these abundances changing?