@Sativa1970 does it literally like it was the 70's. most folk have moved on to either watching the trichs or a combination of checking them when they feel the plant has matured by the look of the pistils.
i normally don't even bother checking trichs until the majority of the plant indicates it is near completed judging by the pistils.
going by pistils alone doesn't always work as a plant can get over mature and lose both terps and potency when it does. the trichs you want to keep will become withered, non-potent, and detach and fall off if left long enough. normally it's not an issue as most growers have a tendency to pull the plants earlier rather than later.
hard core sativas can be harder to call as many never develop a lot of amber trichs, the majority may only get milky. in which case being able to judge maturity by the rest of the plant becomes more important.