Always tempting when one has a nice container but generally speaking I suspect such solutions, unlike typical industrial solutions like acids, are better mixed up as needed. As a rule solutions do not age well and there's the simple physical reality that solutions are more prone to accidents than solids. Would it really be that worth while to pre-mix? I tend to keep solids as such until needed unless something takes a hell of a long time to disolve to saturation. Not an answer to your question per se but something to consider.
Jeremy
