How much NyQuil/DayQuil is ok to take?

I'm legitimately sick, have been for about two days. I've been taking NyQuil/DayQuil because it seems to be the only thing that gives me any real relief from the sore throat and coughing fits. I read on the back of the bottles that you should not take more than 4 "servings" in a 24 hour period. I was wondering if anyone had insight into how legitimate that warning is. I'd been rationing when I'd take it but I just took my fourth for the day and am afraid I won't be able to sleep at all tonight. I have no desire to get high, so if thats what the effect will be I'll p. I just want to be able to sleep while I'm sick. Thanks for your answers.