If your using bagseed then its always safer to wait closer to Week 8 or 9 especially if its more of a sativa then indica. The real weigh is usually put on the last two weeks.

Like Italiano mentioned its all about the trichs. And you can harvest some tops and leave the rest to finish without too much worry about stressing the plant because at 8-9wks they won't have time to go hermi. Just don't cut too early and expect to still grow the plant out for three or four more weeks cause then it can affect yield/quality and have time to pollinate your other plants if you have some. I hate waiting same as you and I am staring at a huge purple wreck top that is just begging me to kill it! I have shake/kief that is about to be gone and then I will get extra ghetto and smoke pipe resin...ick (Don't judge me!) Patience is something I must have ran out of as well.. Good luck!