Hey, you’re likely about half way through flower depending on the strain. Using Trichrome images to determine when it is ready for harvest is exactly what you should do. As the plant gets closer to harvest the tips of the trichromes will start to turn cloudy and then amber.
When you harvest depends on the type of effect you are looking for. I like an energetic high that kicks in quickly so I normally look for ~10% amber trichromes. If you are looking for more of a couch lock you are gonna want more, typically around 30%. But it is all a personal preference. Expire tomorrow a little! Happy growing and good luck!