1. Know how long it can last. A typical high will wear off in about 3 hours, with the main effects spiking about 30 minutes after you smoked. However, when you eat cannabis or take too much, the effect can take longer to wear off.Highs can last as long as 6 hours or more.They can also be unpredictable if the cannabis has other drugs mixed in.t is virtually impossible to instantly sober up after a marijuana high. The chemical delta-9-tetrahydrocannabinol (THC) is the part of weed that makes you high, and it can vary greatly from plant to plant, often depending on how it's grown, processed, and stored; that means that how it affects you can vary greatly.