time to harvest

hi, my small crop have been flowering for 6 weeks and 5 days now and a lot of the smaller buds are 100% golden brown and the top buds are about 70 - 80% golden brown. would it be a good time to harvest now or is it too soon?
Some of the top buds have bean measured at 21 inches long and some 20 inches im not sure what size they should be at this stage?
on the packet of seeds they say the flowering time is 8 weeks but they look like they are ready to chop and they cant stand up properly without supports. most of the lower leaves have shed too. should i wait for another week or chop them now? any advice would be super. thanks