Note that:
$$ \lim_{S\rightarrow \infty} C(t,S) =S-K{\rm e}^{-r(T-t)} $$$$ C(t,S) =S-K{\rm e}^{-r(T-t)} $$
as $S\rightarrow \infty$, for all $t$.
Basically because one can easily accept
$$ \lim_{S\rightarrow \infty} P(t,S) =0 $$$$ P(t,S) =0 $$
as $S\rightarrow \infty$, for all $t$,
and one still expects the put-call parity to hold:
$$ C(t,S) - P(t,S) = S-K{\rm e}^{-r(T-t)} $$
for all $S$.