Now that I've spent some time in emergency departments, I've realised that many people have a warped sense of what an emergency is.
One of the first questions a patient is asked is how long they've had their symptoms for. As soon as you hear "months" (or, God forbid, "years"), you know it's no emergency. Even "weeks" isn't an emergency!
I just don't get these people. Who would be willing to sit in a waiting room at a hospital for several hours, when you could go to a GP or a drop-in medical centre and have it all over in an hour or so?
I'm not concerned about these people taking away valuable medical services from other, sicker people. That's what the triage system is for - when you first arrive at emergency, a nurse gets a brief history and assigns you a triage category, which determines how quickly you're seen, and who's seen before you.
Here's a tip: if you come in with chest pain that you've had for months or years, and you're assigned the lowest triage category and have to wait for hours, it's a fair indication that you have a muscle strain, which is NOT an emergency! (Yes, I saw this patient. He had no emergent symptoms. His chest pain hadn't even worsened that day, or even that week. He was special.)
At the eye hospital, I saw people in emergency who needed a new prescription for their glasses, and that's all. Ever heard of an optometrist? You don't have to wait for 6 hours to see an optometrist! One patient had such mild age-related refractory error (presbyopia) that he didn't even need glasses (though he was wearing some he'd gotten over the counter at the chemist) - however, he was convinced that he was going blind.
There is one caveat though - with kids, trust the parents if they think it's an emergency. They know their kids best, and tend to be good judges of when something is just not right.