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Measurements of the ft values for T=1/2 mirror $\beta$+ decays offer a method to test the conserved vector current hypothesis and to determine Vud, the up-down matrix element of the Cabibbo-Kobayashi-Maskawa matrix. In most mirror decays used for these tests, uncertainties on the ft values are dominated by the uncertainties in the half-lives. Two precision half-life measurements were performed for the T=1/2 $\beta$+ emitters, 17F and 33Cl, in order to eliminate the half-life as the leading source of uncertainty in their ft values. \item[Method] Half-lives of 17F and 33Cl were determined using $\beta$ counting of implanted radioactive ion beam samples on a moving tape transport system at the SPIRAL low energy identification station at GANIL. The 17F half-life result, 64.347~(35) s, precise to $\pm$0.05 %, is a factor of 5 times more precise than the previous world average. The half-life of 33Cl was determined to be 2.5038~(22) s. The current precision of $\pm$0.09 % is nearly 2 times more precise compared to the previous world average. The precision achieved during the present measurements implies that the half-life no longer dominates the uncertainty of the ft values for both T=1/2 mirror decays 17F and 33Cl.

The half-life of the isospin $T=1/2$ mirror ${\ensuremath{\beta}}^{+}$ decay of $^{21}\mathrm{Na}$ was measured at the GANIL-SPIRAL radioactive ion beam facility to be ${T}_{1/2}=22.422$ (10) s, a result that is more than a factor of 5 times more precise than the previous world average, with a resulting $ft$ value that is now two times more precise. The precision of this new result implies that the half-life is no longer the dominant source of uncertainty in the $\mathcal{F}t$ value used in the calculation of ${V}_{\mathrm{ud}}$ from mirror decays to test the conserved vector current hypothesis of the standard model. The value of ${V}_{\mathrm{ud}}$ deduced from mirror decays using the new half-life result is now in better agreement with the ${V}_{\mathrm{ud}}$ derived from $T=1$ superallowed ${0}^{+}$ to ${0}^{+}$ transitions.