Trichomes are of course not the only indicator of when to harvest.
There are other factors that should be taken into account when determining when to harvest.
Calyxes on the plant will swell up, these swollen calyxes are a sign of maturity.
The pistils (what some new growers call hairs) will change colour (often to an orange tinge) and recede into the calyx.
Receding pistils are also a sign of maturity.
Then there is the overall look of the plant. Many experienced growers simply go by this factor, they can determine peak harvest just by looking at the plant and seeing how it looks from afar regarding colour tinge and the look of the calyxes.
All these factors should be taken into account when harvesting. All of these factors usually align when peak harvest approaches.