  We study the evolution in the number density of the highest mass galaxies
over $0.4<z<1.5$ (covering 9 Gyr). We use the Spitzer/HETDEX Exploratory
Large-Area (SHELA) Survey, which covers 17.5 $\mathrm{deg}^2$ with eight
photometric bands spanning 0.3-4.5 $\mu$m within the SDSS Stripe 82 field. This
size produces the lowest counting uncertainties and cosmic variance yet for
massive galaxies at $z\sim1.0$. We study the stellar mass function (SMF) for
galaxies with $\log(M_\ast/M_\odot)>10.3$ using a forward-modeling method that
fully accounts for statistical and systematic uncertainties on stellar mass.
From $z$=0.4 to 1.5 the massive end of the SMF shows minimal evolution in its
shape: the characteristic mass ($M^\ast$) evolves by less than 0.1 dex
($\pm$0.05 dex); the number density of galaxies with $\log (M_\ast/M_\odot)
>11$ stays roughly constant at $\log (n/\mathrm{Mpc}^{-3})$ $\simeq$ $-$3.4
($\pm$0.05), then declines to $\log (n/\mathrm{Mpc}^{-3})$=$-$3.7 ($\pm$0.05)
at $z$=1.5. We discuss the uncertainties in the SMF, which are dominated by
assumptions in the star formation history and details of stellar population
synthesis models for stellar mass estimations. For quiescent galaxies, the data
are consistent with no (or slight) evolution ($\lesssim0.1$ dex) in the
characteristic mass nor number density from $z\sim 1.5$ to the present. This
implies that any mass growth (presumably through "dry" mergers) of the
quiescent massive galaxy population must balance the rate of mass losses from
late-stage stellar evolution and the formation of quenching galaxies from the
star-forming population. We provide a limit on this mass growth from $z=1.0$ to
0.4 of $\Delta M_\ast/M_\ast\leq$ 45% (i.e., $\simeq0.16$ dex) for quiescent
galaxies more massive than $10^{11}$ $M_\odot$.
