You can defiantly harvest in stages if you want. I do think you have at least one week left before you harvest the first round.
My suggestion would be to harvest to top most developed buds first. Then in two week you harvest the rest of the plant. I have found leaving the under developed buds still on the plant for an additional two weeks will help. I do not do this any more because I wash all my lower buds for hash now.
Hope this helps.