well it depends too whats more important the buds or the seeds i know several if they care more about the seeds will let the plant flower like 3-4 weeeks past harvest time to let all the seeds finish the plant might almost be dead but ur seeds should be completely mature brown and almost to falling off the plant
you can peel them open to take a peak.
It takes a minimum of 4 weeks since they were pollinated to mature. You'll get better germination if you let them "age" for a month after harvesting. I store mine in the fridge after in paper envelopes.