What should the half-life be in EWMA when calculating VaR from EWMA?

If we want to calculate an $$x$$-day VaR ($$x$$ is some time period in days) from an Exponentially Weighted Moving Average (EWMA) of vector of returns, what should the half-life in the decay factor in EWMA be?

When calculating the decay factor $$\lambda$$ from the half life $$t_{1/2}$$, we have

$$\lambda = \exp\left(\frac{\log(0.5)}{t_{1/2}}\right)$$

What should $$t_{1/2}$$ be given the VaR period? For example, if we set the VaR period to 10 days, should $$t_{1/2}$$ also be 10 days? If not, why not?