By the time I get them for those things I'm usually sitting at about 4 hours of sleep over the last 48-72(!) hours and unable to eat or (sometimes) even keep water down, so yeah, I need 'em. I wait that long so my body has a change to fight it off without resorting to antibiotics, which sometimes does work. Though also to avoid spending two and a half hours being sick and miserable in the car, at the doctor's office, in the car again, at the pharmacy, then in the car again, rather than at home resting, until I just cannot avoid it.