I would suggest that the amount left in the bottle and how long ago it expired would dictate whether you need it replace it or not. The only thing I keep on hand is long-acting penicillin and it is pretty inexpensive.
^^^ that's all I can think of as well.
What I have on hand no matter what because its all when you need it you need it now is scour hault pepto CD anti LA 200 pen.g and blue coat. I figure all the rest they are not going to die if they have to wait a day to get it.