I have brought up this same reservation dozens of times on similar forums before, and have yet to receive a solid answer on the subject of why half-lives can't decay faster. Perhaps I don't understand it, which is why I will keep making the point until I see evidence to the contrary.
Simple - nuclear decay rate depends upon the physics of the nucleus, which is governed by the strong and weak nuclear forces. The energy scale of these forces is way above that of electromagnetism, that governs the atomic and chemical interactions. Thus, pressure, temperature, electricity, magnetism, etc cannot affect nuclear decay rates unless these reach the energy scale of the nuclear forces (which can occur in relativistic matter, such as in neutron stars and collapsars heading towards black holes.)
The other possibility is to vary the nuclear forces themselves. However, this will not only change decay rates, but destablise otherwise stable nuclei. There is no evidence of this ever happening. On the contrary, evidence from Oklo and other natural nuclear reactors, and from supernovae explosions, demonstrate that nuclear decay rates have been constant over the past several billion years...