By the insurance comment, I just mean that they verify that when you are a freshman you have something, you definitely don't need to bring any forms. It really depends on the availability. There definitely isn't like a 48 hour window as I make and change appointments up until the day before usually. It can be hard to get a same-day appointment, so call as soon as possible (they open at 8am). It all just really depends on how many sick people there are at the time (the year with swine flu was horrendous) and since allergies are hitting everyone hard right now, it might be a little busy. I've never heard of anyone having to wait more than a day, but it depends on your flexibility of scheduling.
It's funny because most people just suffer through illnesses here rather than going, even though we've all already paid for the services. I mean, even if you just have a cold, they'll give you a kit full of all kinds of meds so that you don't have to go buy them. It's a great resource IMO