If the half-life of zithromax (5 day dose pack) is 68 hours, wouldn't that mean that i'm taking more of the medicine each day since it's a daily dose? or is this not necessarily the case? how long would it remain in my system after the last dose?

This is a medicine that can be taken all at once or in separated doses to reduce GI irritation seen in many on the one dose method. The cited half-life can vary some in individuals. It takes about 4 'half-lives' for a drug to me metabolized and leave the body. The desire of treatment is to keep the tissue level of the drug high enough for long enough to kill the germs. Dosing is based on research.