  In the high-scale (split) MSSM, the measured Higgs mass sets an upper bound
on the supersymmetric scalar mass scale MSUSY around $10^{11}$ ($10^{8}$) GeV,
for $\tan\beta$ in the standard range and the central value of the top quark
mass $m_t$. This article discusses how maximal MSUSY is affected by negative
threshold corrections to the quartic Higgs coupling arising from the sbottom
and stop trilinear couplings. In the high-scale MSSM with very high
$\tan\beta$, the electroweak vacuum decay due to the large bottom Yukawa
coupling rules out the possibility of raising MSUSY beyond the above limit. In
cases with large $A_b$ or $A_t$, MSUSY as a common mass of the extra fermions
and scalars can be as high as $10^{17}$ GeV remaining consistent with $m_h$ and
the vacuum longevity if $m_t$ is smaller than the central value by $2\sigma$.
For the central value of $m_t$, the upper limit on MSUSY does not change very
much owing to the metastability, which is the case also in the split MSSM even
with $\pm 2\sigma$ variations in $m_t$.
