As far as I understand, electrons are infinitely stable since they are the least massive particle with non-zero electric charge. However, when accelerated to high-energies, the energy (or mass) of the electrons increases. Does this mean that at sufficient energies it is possible for these electrons to decay (e.g. into a muon, muon antineutrino, and electron neutrino) without scattering off any other particles?
Particle interactions, including decays, must always satisfy energy and momentum conservation in all reference frames. This means that high-energy electrons in an accelerator don't count; to the other electrons traveling down the accelerator with them, everyone is relatively at rest.
An interesting counterexample involves a hard-to-escape reference frame.