[en] We have measured the half-life of the electron-capture (ec) decay of ⁹⁷Ru in a metallic environment, both at low temperature (19 K), and also at room temperature. We find the half-lives at both temperatures to be the same within 0.1%. This demonstrates that a recent claim that the ec decay half-life for ⁷Be changes by 0.9%±0.2% under similar circumstances certainly cannot be generalized to other ec decays. Our results for the half-life of ⁹⁷Ru, 2.8370(14) d at room temperature and 2.8382(14) d at 19 K, are consistent with, but much more precise than, previous room-temperature measurements. In addition, we have also measured the half-lives of the β^--emitters ¹⁰³Ru and ¹⁰⁵Rh at both temperatures, and found them also to be unchanged.