I battled these bastard last year and won gloriously. Here's how I do it. During all stages of flower I check my plants twice daily. Once at sunrise and an hour or two before sunset. If you do this you will see the eggs and you can pick a lot off, but I promise you won't get all of them. If your checking frequently you'll see when the others hatch, pick those off and at dusk spray monterey bt spray on the entire plant. Bt is sensitive to sunlight and will generally die off within 24 to 48 hours after you spray. Do not soak the plant just make sure you covered all the areas. Within 24 hours you will have no more worms except the few dead ones to pick off. This is safe to do all the way up to a week before harvest although I make sure it's atleast two weeks before. Hope this helps.
Edit: to directly answer your question about controlling the months before hand, there really isn't an effective way unless you completely cover the area with mosquito nets, which I do not recommend for many reasons. Mainly because you block sunlight and beneficial insects that could prevent outbreaks of other critters.
