As the trichomes turn amber, the THC begins to degrade. I like to harvest when about 25%-50% are amber. In my opinion, 3/4 amber is way too much. If you want a more heady high, go with all milky and just a tad amber. For more couchlock, wait for at least 25% amber to 50% amber. Some strains are better when harvested earlier, while others need to get some amber to them.