How long does aspirin and tylenol (acetaminophen) stay in ur system? for example usually it says take every 6 hours so does that mean after that it's gone within?

Depends on dose: A one-time dose is normally gone within that time frame. However, regular use of medications create a "steady state" baseline which takes longer to be metabolized. How long depends on your metabolism. For example, kidney or liver disease cause drugs to not be cleared as effectively, and the medication can build up in your system. Also, effects of Aspirin on platelets can last up to a week.