How much more flowering do you think they have left?

Just from the color of the foliage, they're not even starting to finish up! Everything is wonderfully green so you probably have at least 3 weeks to go ... but be checking the trichomes... most people like to see about 30% of them amber - less than that is a more cerebral effect, more than that will tend to a more body effect... and if you go longer than that, you really reduce the amount of THC which is not what most people are looking for in a good smoke! Go grab your microscope or loupe and start checking them out! Good luck - your grow looks amazing!