  Identifying and ameliorating dominant sources of decoherence are important
steps in understanding and improving quantum systems. Here we show that the
free induction decay time ($T_{2}^{*}$) and the Rabi decay rate
($\Gamma_{\mathrm{Rabi}}$) of the quantum dot hybrid qubit can be increased by
more than an order of magnitude by appropriate tuning of the qubit parameters
and operating points. By operating in the spin-like regime of this qubit, and
choosing parameters that increase the qubit's resilience to charge noise (which
we show is presently the limiting noise source for this qubit), we achieve a
Ramsey decay time $T_{2}^{*}$ of $177~\mathrm{ns}$ and a Rabi decay time,
$1/\Gamma_{\mathrm{Rabi}}$, exceeding $1~\mathrm{\mu s}$. We find that the
slowest $\Gamma_{\mathrm{Rabi}}$ is limited by fluctuations in the Rabi
frequency induced by charge noise and not by fluctuations in the qubit energy
itself.
