Every capacitor has a voltage coefficient of capacitance
and for many it is significant. MOS capacitors and junction
capacitors are extremely nonlinear in some regions of
operation and require extra care. Same for polarized
electrolytics and tantalum (also electrolytic) types.
And of course breakdown (preceded by increased
leakage,which is a charge loss) is mighty nonlinear
and probably not the same, the second time either.
At some point you may have to step away from simple
arithmetic and do an integral int(C(V)dV). This point,
seems to be the original question but there is not a
single simple answer until you get to a specific part
and its technology attributes.