With the rain we're having, you could get 8' of growth on a plant that has been pruned to the ground. For an already full and standing plant that is 3'-4' tall, you may get growth of an additional 3-5' this year.

I'm on the North Shore too, near the ocean, and my (40+ years old)privet has been going nuts with new growth. I have already had to shear branches several times this season.