Best way to tell is get a powerful magnifying glass or hand held microscope/w LED to see how far along the trichomes (resin/crystals) are, you just look at the ball tips of the trichomes (looks like golf ball on golf tee). There are three stages 1) clear 2) cloudy 3) amber If they are clear they are still not finished, if they are cloudy they are at peak, and if they are amber/dark they are starting to degrade.
The answer to your question depends on what your looking for in your med's. Clear will be a light heady buzz. Cloudy is the representation of what the strain has to offer at their peak (could be both head & body buzz). Amber is a couch lock heavy buzz, makes you feel like a ten ton heavy thing. So it's really up to you what you want to feel or your patients.