I believe it is mostly dependent on the buck. I have a 7pt on mine that has been done for a month. I also have a 9pt that still has swollen tips on his antlers. I do believe that past this point you won't see much more growth but a little is possible.
I'd say that 85% of the bucks here are done growing. If there is one or two that are slower in developing I still wouldn't expect them to put on any substantial growth...just my .02